自然科学类_2019年GMAT语文高分特训500题【命题分析＋答题攻略＋强化训练】-QQ阅读男生历史网

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◆Passage 1 　　　　　　　　　　　文章结构：观点对比型

Protein synthesis begins when the gene encoding a protein is activated. The gene’s sequence of nucleotides is transcribed into a molecule of messenger RNA (mRNA), which reproduces the information contained in that sequence. Transported outside the nucleus to the cytoplasm, the mRNA is translated into the protein it encodes by an organelle known as a ribosome, which strings together amino acids in the order specified by the sequence of elements in the mRNA molecule. Since the amount of mRNA in a cell determines the amount of the corresponding protein, factors affecting the abundance of mRNA’s play a major part in the normal functioning of a cell by appropriately regulating protein synthesis. For example, an excess of certain proteins can cause cells to proliferate abnormally and become cancerous; a lack of the protein insulin results in diabetes.

Biologists once assumed that the variable rates at which cells synthesize different mRNA’s determine the quantities of mRNA’s and their corresponding proteins in a cell. However, recent investigations have shown that the concentrations of most mRNA’s correlate best, not with their synthesis rate, but rather with the equally variable rates at which cells degrade the different mRNA’s in their cytoplasm. If a cell degrades both a rapidly and a slowly synthesized mRNA slowly, both mRNA’s will accumulate to high levels.

An important example of this phenomenon is the development of red blood cells from their unspecialized parent cells in bone marrow. For red blood cells to accumulate sufficient concentrations of hemoglobin (which transports oxygen) to carry out their main function, the cells’ parent cells must simultaneously produce more of the constituent proteins of hemoglobin and less of most other proteins. To do this, the parent cells halt synthesis of non-hemoglobin mRNA’s in the nucleus and rapidly degrade copies of the non-hemoglobin mRNA’s remaining in the cytoplasm. Halting synthesis of mRNA alone would not affect the quantities of proteins synthesized by the mRNA’s still existing in the cytoplasm. Biologists now believe that most cells can regulate protein production most efficiently by varying both mRNA synthesis and degradation, as developing red cells do, rather than by just varying one or the other.

Questions 1-8 refer to the passage above.

1.The passage is primarily concerned with discussing the

(A) influence of mRNA concentrations on the development of red blood cells.

(B) role of the synthesis and degradation of mRNA in cell functioning.

(D) differences in mRNA concentrations in cell nuclei and in the cytoplasm.　

(E) way in which mRNA synthesis contributes to the onset of diabetes.

2. The passage suggests that a biologist who held the view described in the first sentence of the second paragraph would most probably also have believed which of the following?

(A) The rate of degradation of specific mRNA’s has little effect on protein concentrations.

(B) The rate of degradation of specific mRNA’s should be studied intensively.

(D) Different mRNA’s undergo degradation at widely varying rates.

(E) Most mRNA’s degrade very rapidly.

3. Which of the following best describes the relationship between the second and third paragraphs of the passage?

(A) The second paragraph presents arguments in support of a new theory and the third paragraph presents arguments against that same theory.

(B) The second paragraph describes a traditional view and the third paragraph describes the view that has replaced it on the basis of recent investigations.

(D) The third paragraph describes an investigation that was undertaken to resolve problems raised by phenomena described in the second paragraph.　

(E) Both paragraphs describe in detail specific examples of the phenomenon that is introduced in the first paragraph.

4. The accumulation of concentrations of hemoglobin in red blood cells is mentioned in the passage as an example of which of the following?

(A) The effectiveness of simultaneous variation of the rates of synthesis and degradation of mRNA.

(B) The role of the ribosome in enabling a parent cell to develop properly into a more specialized form.

(D) The abnormal proliferation of a protein that threatens to make the cell cancerous.

(E) The kind of evidence that biologists relied on for support of a view of mRNA synthesis that is now considered obsolete.

5. To begin to control a disease caused by a protein deficiency, the passage suggests that a promising experimental treatment would be to administer a drug that would reduce

(A) only the degradation rate for the mRNA of the protein involved.

(B) only the synthesis rate for the mRNA of the protein involved.

(D) the incidence of errors in the transcription of mRNA’s from genetic nucleotide sequences.

(E) the rate of activity of ribosomes in the cytoplasm of most cells.

6. According to the passage, which of the following best describes the current view on the relationship between the synthesis and the degradation of mRNA in regulating protein synthesis?

(A) Biologists have recently become convinced that the ribosome controls the rates of synthesis and degradation of mRNA.

(B) There is no consensus among biologists as to the significance of mRNA degradation in regulating protein synthesis.

(C) The concept of mRNA degradation is so new that most biologists still believe that the vital role in protein regulation belongs to mRNA synthesis.

(D) Degradation of mRNA is now considered to be the key process and mRNA synthesis is no longer believed to play a significant role.

(E) Degradation of mRNA is now considered to be as important as mRNA synthesis has been, and still is, believed to be.

7. According to the passage, which of the following can happen when protein synthesis is not appropriately regulated?

(A) Diabetes can result from errors that occur when the ribosomes translate mRNA into protein.

(B) Cancer can result from an excess of certain proteins and diabetes can result from an insulin deficiency.

(D) Cancer can be caused by excessively rapid degradation of certain amino acids in the cytoplasm of cells.

(E) Excessive synthesis of one protein can trigger increased degradation of mRNA’s for other proteins and create severe protein imbalances.

8. The passage suggests that a biologist who detected high levels of two proteins in a certain type of cell would be likely to consider which of the following as a possible explanation?

(A) The rate of mRNA degradation for one of the proteins increases as this type of cell develops a more specialized function.

(B) The two proteins are most likely constituents of a complex substance supporting the cells’ specialized function.

(D) The mRNA’s for both proteins are being degraded at a low rate in that type of cell.

(E) The mRNA’s for the two proteins are being synthesized at identical rates in that type of cell.

「词汇装备」

protein n. 蛋白质；朊

synthesis n. 综合，合成；综合体

encoding n. 编码

sequence n. 序列；顺序；续发事件

nucleus n. 核，核心；原子核

molecule n. 分子；微小颗粒，微粒

proliferate v. 增殖；扩散；激增

correlate v. 关联

degrade v. 贬低；使…降级；使…降解

accumulate v. 累积；积聚

simultaneously adv. 同时地

constituent adj. 构成的；选举的

答案详解

1.B 解析主旨题。文章首先对于mRNA的功能进行了介绍，然后叙述了人体对于mRNA的控制机理：开始科学家们认为细胞通过控制各种mRNA的不同速率来控制mRNA的量，但是研究发现提出了不同的假设，最后作者提到现阶段科学家们比较倾向于另一种理论，即：most cells can regulate protein production most efficiently by varying both mRNA synthesis and degradation，所以B项mRNA合成和降解的作用，是本文的主题，故本题选B项。

2.A 解析推断题。第二段第一句中提到的科学家认为：细胞合成各种mRNA的不同速率影响了mRNA量的多少以及相应蛋白质的数量，他们没有认识到降解对于蛋白质浓度的影响，故A项是正确的。

3.C 解析第二段叙述了科学家们不同于原来的一种假设，即：大部分mRNA的浓度并不是和其合成速度，而是和降解其细胞质中mRNA的速度关系最密切，第三段以血红蛋白为例，对这一观点进行了证明，故C项是正确的。

4.A 解析最后一段中，作者提到了红细胞中血红蛋白的浓度，之后作者总结提到：红细胞中血红蛋白的浓度是mRNA的合成和降解同时变化的效果，故A项是正确的。

5.A 解析文章最后一句提到：蛋白质的量决定于其mRNA的合成和降解速率，所以如果要控制一种由蛋白质不足而引起的疾病，那么则要增加蛋白质的量，所以应该减少蛋白质中mRNA的降解速度，故A项是正确的。

6.E 解析推断题。文章最后一句提到：mRNA的合成与降解同时起着重要作用，所以可知E项是正确的。

7.B 解析细节题。第一段最后一句提到：某种蛋白质过多将导致细胞异常增殖以致产生癌变；缺乏蛋白质胰岛素会产生糖尿病，所以可知B项是正确的。

8.D 解析文章第二段最后一句话中提到：如果一细胞慢速降解分别快速和慢速合成的mRNA，两种mRNA都会积累为一很高的浓度，所以可以推测如果一细胞中两种蛋白质的含量都很高，那么两种蛋白质的mRNA的降解过程速率低，故本题应选D项。

◆Passage 2 　　　　　　　　　　　文章结构：观点对比型

Until recently most astronomers believed that the space between the galaxies in our universe was a near perfect vacuum. This orthodox view of the universe is now being challenged by astronomers who believe that a heavy “rain” of gas is falling into many galaxies from the supposedly empty space around them. The gas apparently condenses into a collection of small stars, each a little larger than the planet Jupiter. These stars vastly outnumber the other stars in a given galaxy. The amount of “intergalactic rainfall” into some of these galaxies has been enough to double their mass in the time since they formed. Scientists have begun to suspect that this intergalactic gas is probably a mixture of gases left over from the “big bang” when the galaxies were formed and gas was forced out of galaxies by supernova explosions.

It is well known that when gas is cooled at a constant pressure its volume decreases. Thus, the physicist Fabian reasoned that as intergalactic gas cools, the cooler gas shrinks inward toward the center of the galaxy. Meanwhile its place is taken by hotter intergalactic gas from farther out on the edge of the galaxy, which cools as it is compressed and flows into the galaxy. The net result is a continuous flow of gas, starting as hot gases in inter galactic space and ending as a drizzle of cool gas called a “cooling flow,” falling into the central galaxy.

A fairly heretical idea in the 1970’s, the cooling-flow theory gained support when Fabian observed a cluster of galaxies in the constellation Perseus and found the central galaxy, NGC 1275, to be a strange-looking object with irregular, thin strands of gas radiating from it. According to previous speculation, these strands were gases that had been blown out by an explosion in the galaxy. Fabian, however, disagreed. Because the strands of gas radiating from NGC 1275 are visible in optical photographs, Fabian suggested that such strands consisted not of gas blown out of the galaxy but of cooling flows of gas streaming inward. He noted that the wavelengths of the radiation emitted by a gas would changes as the gas cooled, so that as the gas flowed into the galaxy and became cooler, it would emit not x-rays, but visible light, like that which was captured in the photographs. Fabian’s hypothesis was supported by Canizares’ determination in 1982 that most of the gas in the Perseus cluster was at a temperature of 80 million degrees Kelvin, whereas the gas immediately surrounding NGC 1275 (the subject of the photographs) was at one-tenth this temperature.

Questions 1-7 refer to the passage above.

1.The primary purpose of the passage is to　

(A) illustrate a hypothesis about the origin of galaxies.

(B) provide evidence to dispute an accepted theory about the evolution of galaxies.

(D) report new data on the origins of intergalactic gas.

(E) reconcile opposing views on the formation of intergalactic gas.

2. The author uses the phrase “orthodox view of the universe” (sentence 2) to refer to the belief that

(A) the space between the galaxies is devoid of matter.

(B) the space between galaxies is occupied by stars that cannot be detected by optical photographs.

(D) galaxies contain stars, each the size of Jupiter, which form clusters.

(E) galaxies are being penetrated by gas forced out of other galaxies by supernova explosions.

3. It can be inferred from the passage that, if Fabian is correct, gas in the peripheral regions of a galaxy cluster

(A) streams outward into intergalactic space.

(B) is hotter than gas in the central regions of the galaxy.

(D) results in the creation of unusually large stars.

(E) expands to increase the size of the galaxy.

4. The author of the passage probably mentions Canizares’ determination in order to

(A) clarify an ambiguity in Fabian’s research findings.

(B) illustrate a generalization about the temperature of gas in a galaxy cluster.

(D) provide support for Fabian’ s assertions about the Perseus galaxies.

(E) provide an alternate point of view concerning the movement of gas within a galaxy cluster.D

5. According to the passage, Fabian believes that gas flowing into a central galaxy has which of the following characteristics?

(A) It is one-tenth hotter than it was in the outer regions of the galaxy cluster.

(B) It emits radiation with wavelengths that change as the gas moves toward the center of the galaxy.

(D) It loses 90 percent of its energy as it moves to the center of the galaxy.

(E) It condenses at a rate much slower than the rate of decrease in temperature as the gas flows inward.

6. According to the passage, Fabian’s theory makes use of which of the following principles?

(A) Gas emanating from an explosion will be hotter the more distant it is from the origin.

(B) The wavelength of radiation emitted by a gas as it cools remains constant.

(D) The volume of a gas will increase as the pressure increases.

(E) As gas cools, its density decreases.

7. It can be inferred from the passage that which of the following is true of Fabian’s theory?

(A) It did not receive approval until Canizares’ work was published.

(B) It was not widely accepted in the 1970’s.

(D) It supports earlier speculation that intergalactic gas was largely the result of explosions outside the galaxy.

(E) It was widely challenged until x-ray evidence of gas temperatures in NGC 1275 had been presented.

「词汇装备」

galaxy n. 银河；星系；银河系

vacuum n. 真空；空间；真空吸尘器

orthodox adj. 正统的；传统的；惯常的outnumber v. 数目超过；比…多

intergalactic adj. 星系间的；银河间的

drizzle n. 细雨，毛毛雨

heretical adj. 异端的；异教的

cluster n. 群；簇；丛

constellation n. 星座；星群

hypothesis n. 假设

答案详解

1.B 解析主旨题。文章开始处叙述了星系演变的传统观点，之后对另一种观点进行了介绍。所以可知B项是正确的。

2.A 解析细节题。由第一段第二句“this”一词可知，“正统观点”指文章首句的内容：that the space between the galaxies in our universe was a near perfect vacuum，所以应选A项。

3.B 解析推断题。由第二段最后一句可知，如果Fabian的观点是正确的，那么最终结果是形成了气体流，由星系间热气体开始，以被称作“冷流”的冷气体向星系中心流动结束，所以我们可以推断星系中心的气体的温度要低于星系周围区域的气体，故B项正确。

4.D 解析文章最后一句提到：Fabian的假设在1982年被Canizare的测定所证实，所以可知作者提到Canizare的实验是为了支持Fabian的观点，故D项是正确的。

5.B 解析细节题。第三段第七行中，作者提到：(Fabian) noted that the wavelengths of the radiation emitted by a gas would changes as the gas cooled，故B项是正确的。A项中提到的是Canizare的观测结果，不能任意推广，故不正确。

6.C 解析第二段首句“It is well known that when gas is cooled at a constant pressure its volume decreases”即为Fabian的理论前提，他的假设都是以这一原理为基础推导的，故本题选C项。

7.B 解析细节题。第三段首句提到：A fairly heretical idea in the 1970’s, the cooling-flow theory gained support when…，所以可知Fabian的理论在70年代时并未被广泛接受，故本题应选B项。

◆Passage 3 　　　　　　　　　　　文章结构：现象解释型

Homeostasis, an animal’s maintenance of certain internal variables within an acceptable range, particularly in extreme physical environments, has long interested biologists. The desert rat and the camel in the most water-deprived environments, and marine vertebrates in an all-water environment, encounter the same regulatory problem: maintaining adequate internal fluid balance.

For desert rats and camels, the problem is conservation of water in an environment where standing water is nonexistent, temperature is high, and humidity is low. Despite these handicaps, desert rats are able to maintain the osmotic pressure of their blood, as well as their total body- water content, at approximately the same levels as other rats. One countermeasure is behavioral: these rats stay in burrows during the hot part of the day, thus avoiding loss of fluid through panting or sweating, which are regulatory mechanisms for maintaining internal body temperature by evaporative cooling. Also, desert rats’ kidneys can excrete a urine having twice as high a salt content as seawater.

Camels, on the other hand, rely more on simple endurance. They cannot store water, and their reliance on an entirely unexceptional kidney results in a rate of water loss through renal function significantly higher than that of desert rats. As a result, camels must tolerate losses in body water of up to 30 percent of their body weight. Nevertheless, camels do rely on a special mechanism to keep water loss within a tolerable range: by sweating and panting only when their body temperature exceeds that which would kill a human, they conserve internal water.

Marine vertebrates experience difficulty with their water balance because though there is no shortage of seawater to drink, they must drink a lot of it to maintain their internal fluid balance. But the excess salts from the seawater must be discharged somehow, and the kidneys of most marine vertebrates are unable to excrete a urine in which the salts are more concentrated than in seawater. Most of these animals have special salt-secreting organs outside the kidney that enable them to eliminate excess salt.

Questions 1-3 refer to the passage above.

1. Which of the following most accurately states the purpose of the passage?

(A) To compare two different approaches to the study of homeostasis

(B) To summarize the findings of several studies regarding organisms’ maintenance of internal variables in extreme environments

(D) To cite examples of how homeostasis is achieved by various organisms

(E) To defend a new theory regarding the maintenance of adequate fluid balance Main idea

2. It can be inferred from the passage that some mechanisms that regulate internal body temperature, like sweating and panting, can lead to which of the following?

(A) A rise in the external body temperature

(B) A drop in the body’s internal fluid level

(D) A decrease in the amount of renal water loss

(E) A decrease in the urine’s salt content

3. It can be inferred from the passage that the author characterizes the camel’s kidney as “entirely unexceptional” (sentence 2, para. 3) primarily to emphasize that it

(A) functions much as the kidney of a rat functions

(B) does not aid the camel in coping with the exceptional water loss resulting from the extreme conditions of its environment

(D) is similar in structure to the kidneys of most mammals living in water-deprived environments

(E) requires the help of other organs in eliminating excess salt

「词汇装备」

homeostasis n. 体内平衡

vertebrate n. 脊椎动物

standing water死水

humidity n. 湿度；湿气

burrow n. （兔、狐等的）洞穴；藏身处

evaporative adj. 蒸发的，成为蒸气的

renal adj. 肾脏的，肾的

discharge v. 放出；解雇；卸下

excrete v. 排泄；分泌

答案详解

1.D 解析文章的第一段首先定义平衡，然后指出三种必须在困难环境下保持体内平衡的动物。第二段的中心句是沙漠的老鼠是怎样维持体内平衡的。第三段讨论骆驼是怎样维持体内平衡的，最后一段描述海洋脊椎动物是怎样保持水平衡的。因此，整篇文章的目的就是介绍三种平衡是怎么达到的。由此可知答案为D。

2.B 解析文章开头部分指出沙漠的老鼠通过喘气或流汗来避免液体的流失，这是它们为保持体内温度所进行的调控机制，这些机制降低了体内的温度。接着指出骆驼通过避免流汗或喘气来保持体内水分，除非体内温度非常高。因此，它们必须通过流汗和喘气减少体内水分。因此答案为B。

3.B 解析文章的开头指出在一个缺水，高温而又干燥的环境下，沙漠的老鼠和骆驼都要面临存水的问题。沙漠的老鼠有一个应对机制，但是不包括产生高盐量尿液的肾。作者通过对比发现，骆驼的肾很普通，不能存水。由此可知答案为B。

◆Passage 4 　　　　　　　　　　　　文章结构：结论说明型

Species interdependence in nature confers many benefits on the species involved, but it can also become a point of weakness, when one species involved in the relationship is affected by a catastrophe. Thus, flowering plant species dependent on insect pollination, as opposed to self-pollination or wind pollination, could be endangered when the population of insect-pollinators is depleted by the use of pesticides.

In the forests of New Brunswick, for example, various pesticides have been sprayed in the past 25 years in efforts to control the spruce budworm, an economically significant pest. Scientists have now investigated the effects of the spraying of Matacil, one of the anti-budworm agents that is least toxic to insect-pollinators. They studied Matacil’s effects on insect mortality in a wide variety of wild insect species and on plant fecundity, expressed as the percentage of the total flowers on an individual plant that actually developed fruit and bore seeds. They found that the most pronounced mortality after the spraying of Matacil occurred among the smaller bees and one family of flies, insects that were all important pollinators of numerous species of plants growing beneath the tree canopy of forests. The fecundity of plants in one common indigenous species, the red-osier dogwood, was significantly reduced in the sprayed areas as compared to that of plaints in control plots where Matacil was not sprayed. This species is highly dependent on the insect-pollinators most vulnerable to Matacil. The creeping dogwood, a species similar to the red-osier dogwood, but which is pollinated by large bees, such as bumblebees, showed no significant decline in fecundity. Since large bees are not affected by the spraying of Matacil, these results and weight to the argument that spraying where the pollinators are sensitive to the pesticide used decreases plant fecundity.

The question of whether the decrease in plant fecundity caused by the spraying of pesticides actually causes a decline in the overall population of flowering plant species still remains unanswered. Plant species dependent solely on seeds for survival or dispersal are obviously more vulnerable to any decrease in plant fecundity that occurs, whatever its cause. If, on the other hand, vegetative growth and dispersal (by means of shoots or runners) are available as alternative reproductive strategies for a species, then decreases in plant fecundity may be of little consequence. The fecundity effects described here are likely to have the most profound impact on plant species with all four of the following characteristics: a short life span, a narrow geographic range, an incapacity for vegetative propagation, and a dependence on a small number of insect-pollinator species. Perhaps we should give special attention to the conservation of such plant species since they lack key factors in their defenses against the environmental disruption caused by pesticide use.

Questions 1-7 refer to the passage above.

1. Which of the following best summarizes the main point of the passage?

(A) Species interdependence is a point of weakness for some plants, but is generally beneficial to insects involved in pollination.

(B) Efforts to control the spruce budworm have had deleterious effects on the red-osier dogwood.

(D) The spraying of pesticides can reduce the fecundity of a plant species, but probably does not affect its overall population stability.

(E) Plant species lacking key factors in their defenses against human environmental disruption will probably become extinct.

2. According to the author, a flowering plant species whose fecundity has declined due to pesticide spraying may not experience an overall population decline if the plant species can do which of the following?

(A) Reproduce itself by means of shoots and runners.

(B) Survive to the end of the growing season.

(D) Respond to the fecundity decline by producing more flowers.

(E) Attract large insects as pollinators.

3. The passage suggests that the lack of an observed decline in the fecundity of the creeping dogwood strengthens the researchers conclusions regarding pesticide use because the

(A) creeping dogwood is a species that does not resemble other forest plants.

(B) creeping dogwood is a species pollinated by a broader range of insect species than are most dogwood species.

(C) creeping dogwood grows primarily in regions that were not sprayed with pesticide, and so served as a control for the experiment.

(D) creeping dogwood is similar to the red-osier dogwood, but its insect pollinators are known to be insensitive to the pesticide used in the study.

(E) geographical range of the creeping dogwood is similar to that of the red-osier dogwood, but the latter species relies less on seeds for reproduction.

4. The passage suggests that which of the following is true of the forest regions in New Brunswick sprayed with most anti-budworm pesticides other than Matacil?

(A) The fecundity of some flowering plants in those regions may have decreased to an even greater degree than in the regions where Matacil is used.

(B) Insect mortality in those regions occurs mostly among the larger species of insects, such as bumblebees.

(C) The number of seeds produced by common plant, species in those regions is probably comparable to the number produced where Matacil is sprayed.

(D) Many more plant species have become extinct in those regions than in the regions where Matacil is used.

(E) The spruce budworm is under better control in those regions than in the regions where Matacil is sprayed.

5. It can be inferred that which of the following is true of plant fecundity as it is defined in the passage?

(A) A plant’s fecundity decreases as the percentage of unpollinated flowers on the plant increases.

(B) A plant’s fecundity decreases as the number of flowers produced by the plant decreases.

(D) A plant’s fecundity is usually low if the plant relies on a small number of insect species for pollination.

(E) A plant’s fecundity is high if the plant can reproduce quickly by means of vegetative growth as well as by the production of seeds.

6. It can be inferred from the passage that which of the following plant species would be LEAST likely to experience a decrease in fecundity as a result of the spraying of a pesticide not directly toxic to plants?

(A) A flowering tree pollinated by only a few insect species.

(B) A kind of insect-pollinated vine producing few flowers.

(D) A flowering shrub pollinated by a large number of insect species.

(E) A type of wildflower typically pollinated by larger insects.

7. Which of the following assumptions most probably underlies the author’s tentative recommendation in the last sentence?

(A) Human activities that result in environmental disruption should be abandoned.

(B) The use of pesticides is likely to continue into the future.

(D) Preventing the endangerment of a species is less costly than trying to save an already endangered one.

(E) Conservation efforts aimed at preserving a few well-chosen species are more cost-effective than are broader based efforts to improve the environment.

「词汇装备」

catastrophe n. 大灾难；大祸；惨败

self-pollination n. 自花授粉

pollination n. 授粉（作用）

budworm n. 蚜虫

fecundity n. 繁殖力；多产；肥沃

indigenous adj. 本土的；土著的；固有的

dispersal n. 分散；传播；散布

vegetative propagation营养（体）繁殖，无性繁殖

答案详解

1.C 解析主旨题。第一段第二句话为本文的主题句：flowering plant species dependent on insect pollination, as opposed to self-pollination or wind pollination, could be endangered when the population of insect-pollinators is depleted by the use of pesticides，之后作者都是在围绕这一主题进行叙述，故本题应选C项。

2.A 解析细节题。文章第三段中提到：If…vegetative growth and dispersal (by means of shoots or runners) are available as alternative reproductive strategies for a species, then decreases in plant fecundity may be of little consequence，故若植物通过芽繁殖，那么其种群数量不会受到杀虫剂的太大影响，所以本题选A。

3.D 解析推断题。第二段结尾处，作者提到了creeping dogwood，指出它和red-osier dogwood相近，但因为其传粉昆虫对杀虫剂不敏感，其有性生殖力便没有显著下降，所以本题应该选择D项。

4.A 解析推断题。第二段第二句中提到“Matacil, one of the anti-budworm agents that is least toxic to insect-pollinators…”之后作者叙述了其对于植物传粉的影响。所以可以推测如果在森林中喷洒了Matacil之外的杀虫剂那么对某些植物的有性生殖力的影响可能更大，故A项正确。

5.A 解析细节题。文章第二段对于plant fecundity进行了定义，即“the percentage of the total flowers on an individual plant that actually developed fruit and bore seeds”，根据此定义可知A项是正确的。

6.B 解析推断题。第二段提到：Plant species dependent solely on seeds for survival or dispersal are obviously more vulnerable to any decrease in plant fecundity that occurs，所以推断风媒植物因为不依靠昆虫传粉，所以喷洒杀虫剂对其几乎没有影响，故本题应选B项。

7.B 解析最后一句中作者表示：或许我们应特别关注保护上述几种植物，因为它们缺少对付杀虫剂引起的生存环境变化的有效手段。所以若要继续使用杀虫剂的话，作者的建议会被更加重视，所以本题应选B项。

◆Passage 5 　　　　　　　　　　　　文章结构：现象解释型

In addition to conventional galaxies, the universe contains very dim galaxies that until recently went unnoticed by astronomers. Possibly as numerous as conventional galaxies, these galaxies have the same general shape and even the same approximate number of stars as a common type of conventional galaxy, the spiral, but tend to be much larger. Because these galaxies’ mass is spread out over larger areas, they have far fewer stars per unit volume than do conventional galaxies. Apparently these low-surface-brightness galaxies, as they are called, take much longer than conventional galaxies to condense their primordial gas and convert it to stars—that is, they evolve much more slowly. These galaxies may constitute an answer to the long-standing puzzle of the missing baryonic mass in the universe. Baryons-subatomic particles that are generally protons or neutrons—are the source of stellar, and therefore galactic, luminosity, and so their numbers can be estimated based on how luminous galaxies are. However, the amount of helium in the universe, as measured by spectroscopy, suggests that there are far more baryons in the universe than estimates based on galactic luminosity indicate. Astronomers have long speculated that the missing baryonic mass might eventually be discovered in intergalactic space or as some large population of galaxies that are difficult to detect.

Questions 1-7 refer to the passage above.

1. According to the passage, conventional spiral galaxies differ from low-surface-brightness galaxies in which of the following ways?

(A) They have fewer stars than do low-surface-brightness galaxies.

(B) They evolve more quickly than low-surface-brightness galaxies.

(D) They contain less helium than do low-surface-brightness galaxies.

(E) They are larger than low-surface-brightness galaxies.

2. It can be inferred from the passage that which of the following is an accurate physical description of typical low-surface-brightness galaxies?

(A) They are large spiral galaxies containing fewer stars than do conventional galaxies.

(B) They are compact but very dim spiral galaxies.

(D) They are small, young spiral galaxies that contain a high proportion of primordial gas.

(E) They are large, dense spirals with low luminosity.

3. It can be inferred from the passage that the “long-standing puzzle” refers to which of the following?

(A) The difference between the rate at which conventional galaxies evolve and the rate at which low-surface-brightness galaxies evolve

(B) The discrepancy between estimates of total baryonic mass derived from measuring helium and estimates based on measuring galactic luminosity

(C) The inconsistency between the observed amount of helium in the universe and the number of stars in typical low-surface-brightness galaxies

(D) Uncertainties regarding what proportion of baryonic mass is contained in intergalactic space and what proportion in conventional galaxies

(E) Difficulties involved in detecting very distant galaxies and in investigating their luminosity

4. The author implies that low-surface-brightness galaxies could constitute an answer to the puzzle discussed in the second paragraph primarily because

(A) they contain baryonic mass that was not taken into account by researchers using galactic luminosity to estimate the number of baryons in the universe

(B) they, like conventional galaxies that contain many baryons, have evolved from massive, primordial gas clouds

(C) they may contain relatively more helium, and hence more baryons, than do galaxies whose helium content has been studied using spectroscopy

(D) they have recently been discovered to contain more baryonic mass than scientists had thought when low-surface-brightness galaxies were first observed

(E) they contain stars that are significantly more luminous than would have been predicted on the basis of initial studies of luminosity in low-surface-brightness galaxies

5. The author mentions the fact that baryons are the source of stars’ luminosity primarily in order to explain

(A) how astronomers determine that some galaxies contain fewer stars per unit volume than do others

(B) how astronomers are able to calculate the total luminosity of a galaxy

(D) why astronomers’ estimates of baryonic mass based on galactic luminosity are more reliable than those based on spectroscopic studies of helium

(E) how astronomers know bright galaxies contain more baryons than do dim galaxies

6. The author of the passage would be most likely to disagree with which of the following statements?

(A) Low-surface-brightness galaxies are more difficult to detect than are conventional galaxies.

(B) Low-surface-brightness galaxies are often spiral in shape.

(D) Astronomers have devised a useful way of estimating the total baryonic mass in the universe.

(E) Astronomers have discovered a substantial amount of baryonic mass in intergalactic space.

7.The primary purpose of the passage is to

(A) describe a phenomenon and consider its scientific significance

(B) contrast two phenomena and discuss a puzzling difference between them

(D) compare two classes of objects and discuss the physical properties of each

(E) discuss a discovery and point out its inconsistency with existing theory

「词汇装备」

dim adj. 暗淡的，昏暗的

condense v. 浓缩；凝结

particle n. 颗粒；质点；极小量

luminous adj. 发光的；明亮的；清楚的

spectroscopy n. 光谱学

galactic adj. 银河的；乳汁的

luminosity n. 光度；光明；光辉

intergalactic adj. 星系间的；银河间的

答案详解

1.B 解析第一段介绍了传统的暗星系和低表面亮度星系。接着指出，昏暗星系是传统星系的一种类型，有着大致相同数量的恒星，但因为分布在更广泛的领域，因此往往更大，更具有弥漫性。文章还表明，暗星系比传统星系花费更多的时间将原始气体形成恒星，这意味着暗星系的演化过程比传统星系慢得多。由此可知，B项为正确答案。

2.C 解析第一段比较了暗星系和传统星系。暗星系与传统星系里的螺旋星系有着相同的形状，表明暗星系是螺旋形的。文章还表明尽管两者有相同数量的星星，暗星系比传统星系更大，占据的空间更广。由此可见C项为正确答案。

3.B 解析第二段描述了失踪的重子物质的宇宙中的未解之谜。文章指出，重子是星系光度的来源，所以科学家通过测量星系的光度来估算出宇宙中的重子质量。令人困惑的是，宇宙中的氦光谱测量表明，宇宙中的重子质量比措施的亮度高得多。因此可知B项与原文相符。

4.A 解析令人困惑的是，基于亮度的宇宙重子质量的估计低于那些基于光谱的估价。文章指出，天文学家们直到最近才注意到暗星系，而这些星系可能有助于解释宇宙的失踪重子质量。文章还建议天文学家测量特定的星系光度。由此可以推断，和天文学家以前的发现相比，这些星系的光度没有测量，亮度的估计没有考虑重子的质量。因此A选项为正确答案。

5.C 解析第二段介绍了科学家们一直疑惑宇宙中失踪重子的质量（用亮度可以测量它）。鉴于重子是星系的亮度源，天文学家可以通过测量它的光度来估计星系的重子质量。因此可知C项为正确答案。

6.E 解析第二段指出，对于天文学家们对宇宙重子质量的估计结果，用光度测量比用光谱测量比较低。最后一句指出，天文学家推测失踪重子的质量可能会在星系际空间或难以检测的星系被发现。虽然暗星系和低表面亮度星系可能有助于解释失踪重子质量的问题，文章没有提供证据显示在星际空间发现重子质量的可能性。由此可知E项为正确答案。

7.A 解析第一段描述了一种现象：暗星系的发现和它们的一般属性。第二段介绍了这个发现将怎样帮助天文学家解决一个长期存在的关于宇宙的重子质量难题。由此可知A项为正确答案。

◆Passage 6 　　　　　　　　　　　文章结构：结论说明型

Although genetic mutations in bacteria and viruses can lead to epidemics, some epidemics are caused by bacteria and viruses that have undergone no significant genetic change. In analyzing the latter, scientists have discovered the importance of social and ecological factors to epidemics. Poliomyelitis, for example, emerged as an epidemic in the United States in the twentieth century; by then, modern sanitation was able to delay exposure to polio until adolescence or adulthood, at which time polio infection produced paralysis. Previously, infection had occurred during infancy, when it typically provided lifelong immunity without paralysis. Thus, the hygiene that helped prevent typhoid epidemics indirectly fostered a paralytic polio epidemic. Another example is Lyme disease, which is caused by bacteria that are transmitted by deer ticks. It occurred only sporadically during the late nineteenth century but has recently become prevalent in parts of the United States, largely due to an increase in the deer population that occurred simultaneously with the growth of the suburbs and increased outdoor recreational activities in the deer’s habitat. Similarly, an outbreak of dengue hemorrhagic fever became an epidemic in Asia in the 1950s because of ecological changes that caused Aedes aegypti, the mosquito that transmits the dengue virus, to proliferate. The stage is now set in the United States for a dengue epidemic because of the inadvertent introduction and wide dissemination of another mosquito, Aedes albopictus.

Questions 1-6 refer to the passage above.

1. The passage suggests that a lack of modern sanitation would make which of the following most likely to occur

(A) An outbreak of Lyme disease

(B) An outbreak of dengue hemorrhagic fever

(D) An epidemic of paralytic polio among infants

(E) An epidemic of paralytic polio among adolescents and adults

2. According to the passage, the outbreak of dengue hemorrhagic fever in the 1950s occurred for which of the following reasons?

(A) The mosquito Aedes aegypti was newly introduced into Asia.

(B) The mosquito Aedes aegypti became more numerous.

(D) Individuals who would normally acquire immunity to the dengue virus as infants were not infected until later in life.

(E) More people began to visit and inhabit areas in which mosquitoes live and breed.

3. It can be inferred from the passage that Lyme disease has become prevalent in parts of the United States because of which of the following?

(A) The inadvertent introduction of Lyme disease bacteria to the United States

(B) The inability of modern sanitation methods to eradicate Lyme disease bacteria

(D) The spread of Lyme disease bacteria from infected humans to noninfected humans

(E) An increase in the number of humans who encounter deer ticks

4. Which of the following can most reasonably be concluded about the mosquito Aeries albopictus on the basis of information given in the passage?

(A) It is native to the United States.

(B) It can proliferate only in Asia.

(D) It caused an epidemic of dengue hemorrhagic fever in the 1950s.

(E) It replaced Aedes aegypti in Asia when ecological changes altered Aedes aegypti’s habitat.

5. Which of the following best describes the organization of the passage?

(A) A paradox is stated, discussed, and left unresolved.

(B) Two opposing explanations are presented, argued, and reconciled.

(D) A generalization is stated and is then followed by three instances that support the generalization.

(E) An argument is described and is then followed by three counterexamples that refute the argument.

6. Which of the following, if true, would most strengthen the author’s assertion about the cause of the Lyme disease outbreak in the United States?

(A) The deer population was smaller in the late nineteenth century than in the mid twentieth century.

(B) Interest in outdoor recreation began to grow in the late nineteenth century.

(D) Outdoor recreation enthusiasts routinely take measures to protect themselves against Lyme disease.

(E) Scientists have not yet developed a vaccine that can prevent Lyme disease.

「词汇装备」

mutation n. 突变；变化

epidemic n. 传染病；流行病

sanitation n. 卫生系统或设备

paralysis n. 麻痹；无力；停顿

sporadically adv. 零星地；偶发地

inadvertent adj. 疏忽的；不注意的

dissemination n. 宣传；散播；传染（病毒）

答案详解

1.C 解析文章的中间部分介绍了现代的卫生条件在延缓小儿麻痹症的发作方面的作用，接着指出卫生条件防止了流感的发生，而这种流感可以导致麻痹性脊髓灰质炎的流行。因此可以推断出如果缺少现代的卫生条件，可能导致流感的发生。由此可知C项为正确答案。

2.B 解析文章中间部分讨论了20世纪50年代登革出血热的爆发，在亚洲变成了一场传染性的疾病。原因是生态变化导致了埃及伊蚊的滋生，这种蚊子可以传播登革病毒并增加病毒的繁殖。由此可知B项为正确答案。

3.B 解析文章中间部分指出这种疾病是由鹿蜱所携带的病菌引起的；由于鹿的数量有所增加，这种疾病在美国很流行。同时，郊区在扩展，在鹿的栖息地户外活动有所增加。由此可以推断处更多的人遇到携带病毒的鹿蜱。因此选E项。

4.C 解析文章的最后一句指出白纹伊蚁偶然引入到了美国并且广泛传播，因此美国一时盛行登革热。由此可以推断出这种蚊子可以传播登革病毒。因此C项为正确答案。

5.D 解析文章首先指出一些传染病不是由细胞和病毒的基因突变引起的，而是因为环境中社会和经济的变化。例如：小儿麻痹症，莱姆病和登革出血热说明了这一观点。D项与文章相符。

6.A 解析作者认为最近莱姆病的流行是因为鹿的数量的增加和郊区的扩展，人们在鹿的栖息地呆的时间比较长。上世纪90年代，莱姆病只是零星地出现。由此可知A项为正确答案。

◆Passage 7　　　　　　　　　　　　文章结构：观点对比型

No very satisfactory account of the mechanism that caused the formation of the ocean basins has yet been given. The traditional view supposes that the upper mantle of the earth behaves as a liquid when it is subjected to small forces for long periods and that differences in temperature under oceans and continents are sufficient to produce convection in the mantle of the earth with rising convection currents under the mid-ocean ridges and sinking currents under the continents. Theoretically, this convection would carry the continental plates along as though they were on a conveyor belt and would provide the forces needed to produce the split that occurs along the ridge. This view may be correct: it has the advantage that the currents are driven by temperature differences that themselves depend on the position of the continents. Such a back-coupling, in which the position of the moving plate has an impact on the forces that move it, could produce complicated and varying motions.

On the other hand, the theory is implausible because convection does not normally occur along lines, and it certainly does not occur along lines broken by frequent offsets or changes in direction, as the ridge is. Also it is difficult to see how the theory applies to the plate between the Mid-Atlantic Ridge and the ridge in the Indian Ocean. This plate is growing on both sides, and since there is no intermediate trench, the two ridges must be moving apart. It would be odd if the rising convection currents kept exact pace with them. An alternative theory is that the sinking part of the plate, which is denser than the hotter surrounding mantle, pulls the rest of the plate after it. Again it is difficult to see how this applies to the ridge in the South Atlantic, where neither the African nor the American plate has a sinking part.

Another possibility is that the sinking plate cools the neighboring mantle and produces convection currents that move the plates. This last theory is attractive because it gives some hope of explaining the enclosed seas, such as the Sea of Japan. These seas have a typical oceanic floor, except that the floor is overlaid by several kilometers of sediment. Their floors have probably been sinking for long periods. It seems possible that a sinking current of cooled mantle material on the upper side of the plate might be the cause of such deep basins. The enclosed seas are an important feature of the earth’s surface, and seriously require explanation because, in addition to the enclosed seas that are developing at present behind island arcs, there are a number of older ones of possibly similar origin, such as the Gulf of Mexico, the Black Sea, and perhaps the North sea.

Questions 1-8 refer to the passage above.

1. According to the traditional view of the origin of the ocean basins, which of the following is sufficient to move the continental plates?

(A) Increases in sedimentation on ocean floors.

(B) Spreading of ocean trenches.

(D) Sinking of ocean basins.

(E) Differences in temperature under oceans and continents.

2. It can be inferred from the passage that, of the following, the deepest sediments would be found in the

(A) Indian Ocean.

(B) Black Sea.

(D) South Atlantic.

(E) Pacific.

3. The author refers to a “conveyor belt” in order to

(A) illustrate the effects of convection in the mantle.

(B) show how temperature differences depend on the positions of the continents.

(D) describe the complicated motions made possible by back-coupling.

(E) account for the rising currents under certain mid-ocean ridges.

4. The author regards the traditional view of the origin of the oceans with

(A) slight apprehension.

(B) absolute indifference.

(D) complete disbelief.

(E) guarded skepticism.

5. According to the passage, which of the following are separated by a plate that is growing on both sides?

(A) The Pacific Ocean and the Sea of Japan.

(B) The South Atlantic Ridge and the North Sea Ridge.

(D) The Mid-Atlantic Ridge and the Indian Ocean Ridge.

(E) The Black Sea and the Sea of Japan.

6. Which of the following, if it could be demonstrated, would most support the traditional view of ocean formation?

(A) Convection usually occurs along lines.

(B) The upper mantle behaves as a dense solid.

(D) Sinking plates cool the mantle.

(E) Island arcs surround enclosed seas.

7. According to the passage, the floor of the Black sea can best be compared to a

(A) rapidly moving conveyor belt.

(B) slowly settling foundation.

(D) violently erupting volcano.

(E) slowly eroding mountain.

8. Which of the following titles would best describe the content of the passage?

(A) A Description of the Oceans of the World

(B) Several Theories of Ocean Basin Formation

(D) Convection and Ocean Currents

(E) Temperature Differences Among the Oceans of the World

「词汇装备」

mantle n. 地幔；斗篷；覆盖物

convection n. 对流；传送

theoretically adv. 理论地；理论上

sediment n. 沉积；沉淀物

implausible adj. 难以置信的，不像真实的

offset n. 抵消，补偿

答案详解

1.E 解析细节题。题目问传统观点中，哪个因素推动板块的流动，通过关键词“traditional view”定位到第一段第二句，由此可知，洋底地幔和陆底地幔的温差造成地幔的对流，故E项是正确的。

2.B 解析推断题。文章最后一段中提到：日本海、墨西哥湾、黑海等内海是因为沉积物的覆盖而形成的，故B项是正确的。A、C、D、E四项都不是内海的例子。

3.A 解析推断题。作者在第一段第三句中提到了“conveyor belt”，该句的前半句提到地幔中的对流会推动板块的移动，然后作者以传送带为例，对此进行了描述，故A项是正确的。

4.E 解析态度题。针对传统观点，在第一段第四句中，作者提到“This view may be correc”，在第二段第一句中作者又提到“…the theory is implausible…”，所以可知作者对于传统观点的态度是谨慎的怀疑，故E项是正确的。

5.D 解析细节题。根据题干关键词“separated，growing on both sides”定位到第二段第2第三句，故本题应选D项。

6.A 解析文章第二段第一句中提到：On the other hand, the theory is implausible because convection does not normally occur along lines，所以可知传统观点认为对流通常沿直线产生，故A项可以支持传统的大洋构造观点。

7.B 解析文章第三段中作者提到日本海，并提到内海的特点“Their floors have probably been sinking for long periods.”，然后作者说黑海的海底成因也是如此，故B项缓慢建立的基础可以用来形容黑海，故本题应选B项。A项快速移动的传送带是用来比喻地幔中的对流的，C、D、E三项文中没有涉及。

8.B 解析主旨题。文章第一句“No very satisfactory account of the mechanism that caused the formation of the ocean basins has yet been given.”即指出关于海盆的成因，现在都没有一个令人满意的解释，之后作者提出了可能的三种解释，并分别做了评价，故B项是正确的。

◆Passage 8　　　　　　　　　　　　文章结构：问题回答型

Virtually everything astronomers known about objects outside the solar system is based on the detection of photons-quanta of electromagnetic radiation. Yet there is another form of radiation that permeates the universe: neutrinos. With (as its name implies) no electric charge, and negligible mass, the neutrino interacts with other particles so rarely that a neutrino can cross the entire universe, even traversing substantial aggregations of matter, without being absorbed or even deflected. Neutrinos can thus escape from regions of space where light and other kinds of electromagnetic radiation are blocked by matter. Furthermore, neutrinos carry with them information about the site and circumstances of their production: therefore, the detection of cosmic neutrinos could provide new information about a wide variety of cosmic phenomena and about the history of the universe.

But how can scientists detect a particle that interacts so infrequently with other matter? Twenty-five years passed between Pauli’s hypothesis that the neutrino existed and its actual detection: since then virtually all research with neutrinos has been with neutrinos created artificially in large particle accelerators and studied under neutrino microscopes. But a neutrino telescope, capable of detecting cosmic neutrinos, is difficult to construct. No apparatus can detect neutrinos unless it is extremely massive, because great mass is synonymous with huge numbers of nucleons (neutrons and protons), and the more massive the detector, the greater the probability of one of its nucleon’s reacting with a neutrino. In addition, the apparatus must be sufficiently shielded from the interfering effects of other particles.

Fortunately, a group of astrophysicists has proposed a means of detecting cosmic neutrinos by harnessing the mass of the ocean. Named DUMAND, for Deep Underwater Muon and Neutrino Detector, the project calls for placing an array of light sensors at a depth of five kilometers under the ocean surface. The detecting medium is the seawater itself: when a neutrino interacts with a particle in an atom of seawater, the result is a cascade of electrically charged particles and a flash of light that can be detected by the sensors. The five kilometers of seawater above the sensors will shield them from the interfering effects of other high-energy particles raining down through the atmosphere.

The strongest motivation for the DUMAND project is that it will exploit an important source of information about the universe. The extension of astronomy from visible light to radio waves to x-rays and gamma rays never failed to lead to the discovery of unusual objects such as radio galaxies, quasars, and pulsars. Each of these discoveries came as a surprise. Neutrino astronomy will doubtless bring its own share of surprises.

Questions 1-9 refer to the passage above.

1. Which of the following titles best summarizes the passage as a whole?

(A) At the Threshold of Neutrino Astronomy

(B) Neutrinos and the History of the Universe

(D) The DUMAND System and How It Works

(E) The Properties of the Neutrino

2. With which of the following statements regarding neutrino astronomy would the author be most likely to agree?

(A) Neutrino astronomy will supersede all present forms of astronomy.

(B) Neutrino astronomy will be abandoned if the DUMAND project fails.

(D) Neutrino astronomy will disclose phenomena that will be more surprising than past discoveries.

(E) Neutrino astronomy will always be characterized by a large time lag between hypothesis and experimental confirmation.

3. In the last paragraph, the author describes the development of astronomy in order to

(A) suggest that the potential findings of neutrino astronomy can be seen as part of a series of astronomical successes.

(B) illustrate the role of surprise in scientific discovery.

(D) name some cosmic phenomena that neutrino astronomy will illuminate.

(E) contrast the motivation of earlier astronomers with that of the astrophysicists working on the DUMAND project.

4. According to the passage, one advantage that neutrinos have for studies in astronomy is that they

(A) have been detected for the last twenty-five years.

(B) possess a variable electric charge.

(D) carry information about their history with them.

(E) are very similar to other electromagnetic particles.

5. According to the passage, the primary use of the apparatus mentioned in para. 2 would be to

(A) increase the mass of a neutrino.

(B) interpret the information neutrinos carry with them.

(D) see neutrinos in distant regions of space.

(E) detect the presence of cosmic neutrinos.

6. The passage states that interactions between neutrinos and other matter are

(A) rare.

(B) artificial.

(D) unpredictable.

(E) hazardous.

7. The passage mentions which of the following as a reason that neutrinos are hard to detect?

(A) Their pervasiveness in the universe.

(B) Their ability to escape from different regions of space.

(D) The similarity of their structure to that of nucleons.

(E) The infrequency of their interaction with other matter.

8. According to the passage, the interaction of a neutrino with other matter can produce

(A) particles that are neutral and massive.

(B) a form of radiation that permeates the universe.

(D) charged particles and light.

(E) a situation in which light and other forms of electromagnetic radiation are blocked.

9. According to the passage, one of the methods used to establish the properties of neutrinos was

(A) detection of photons.

(B) observation of the interaction of neutrinos with gamma rays.

(D) measurement of neutrinos that interacted with particles of seawater.

(E) experiments with electromagnetic radiation.

「词汇装备」

solar adj. 太阳的；日光的

electromagnetic adj. 电磁的

permeate v. 渗透，透过；弥漫

aggregation n. 聚集；聚集体

deflect v. 使转向；使偏斜；使弯曲

apparatus n. 装置，设备；仪器

shield v. 遮蔽；包庇；避开

harness v. 治理；利用

cascade n. 层叠；小瀑布；喷流

答案详解

1.A 解析主旨题。文章开始处对于中微子对于天体观测的重要性进行了叙述，最后又指出对中微子进行观测的原因就是它能提供有关宇宙的重要信息。所以总的来看，本文中对于中微子的考查以及研究都是为了天文学服务的，故A项的表述是正确的。作者研究中微子是为了为天文学做贡献，所以C项表述过于片面。

2.C 解析文章最后一句提到“Neutrino astronomy will doubtless bring its own share of surprises”，说明作者认为中微子天文学将带来天文学领域的重大变革，故本题应选C项。

3.A 解析推断题。最后一段中作者叙述了一系列天文学的发展，然后得出结论“Neutrino astronomy will doubtless bring its own share of surprises”，可以推断，作者认为中微子天文学的未来成果可以被看做天文学的一系列成果之一，故A项的表述是正确的。

4.D 解析文章第一段结尾处提到“neutrinos carry with them information about the site and circumstances of their production”因此对中微子的观察可以提供宇宙中一些现象以及宇宙起源的新信息，所以可知D项是正确的。A项文中没有提到；B、C、E三项是错误的。

5.E 解析细节题。第二段作者提到了“apparatus”，联系前后文可知，该仪器是指中微子望远镜，根据“No apparatus can detect neutrinos unless it is extremely massive”一句可知，该仪器的主要用途是探测中微子，故E项是最准确的。

6.A 解析细节题。根据第一段the neutrino interacts with other particles so rarely…，可知中微子很少与其他物质反应，故本题应选A项。

7.E 解析文章第二段第一句提到“But how can scientists detect a particle that interacts so infrequently with other matter?”可知，因为中微子与其他物质的反应少，所以它很难被直接观察到，故本题应选E项。

8.D 解析细节题。第三段倒数第二句提到：when a neutrino interacts with a particle in an atom of seawater, the result is a cascade of electrically charged particles and a flash of light，所以可知中微子和其他物质反应可产生带电粒子和光，故本题应选D项。

9.C 解析细节题。文章第二段第二句中提到：…all research with neutrinos has been with neutrinos created artificially in large particle accelerators and studied under neutrino microscopes…，所以确定中微子性质的一种方法是观测人造的中微子，故C项正确。

◆Passage 9 　　　　　　　　　　　文章结构：问题回答型

All of the cells in a particular plant start out with the same complement of genes. How then can these cells differentiate and form structures as different as roots, stems, leaves, and fruits? The answer is that only a small subset of the genes in a particular kind of cell are expressed, or turned on, at a given time. This is accomplished by a complex system of chemical messengers that in plants include hormones and other regulatory molecules. Five major hormones have been identified: auxin, abscisicacid, cytokinin, ethylene, and gibberellin. Studies of plants have now identified a new class of regulatory molecules called oligosaccharide.

Unlike the oligosaccharide, the five well-known plant hormones are pleiotropic rather than specific, that is, each has more than one effect on the growth and development of plants. The five has so many simultaneous effects that they are not very useful in artificially controlling the growth of crops. Auxin, for instance, stimulates the rate of cell elongation, causes shoots to grow up and roots to grow down, and inhibits the growth of lateral shoots. Auxin also causes the plant to develop a vascular system, to form lateral roots, and to produce ethylene.

The pleiotropy of the five well-studied plant hormones is somewhat analogous to that of certain hormones in animal. For example, hormones from the hypothalamus in the brain stimulate the anterior lobe of the pituitary gland to synthesize and release many different hormones, one of which stimulates the release of hormones from the adrenal cortex. These hormones have specific effects on target organs all over the body. One hormone stimulates the thyroid gland, for example, another the ovarian follicle cells, and so forth. In other words, there is a hierarchy of hormones.

Such a hierarchy may also exist in plants. Oligosaccharides are fragments of the cell wall released by enzymes: different enzymes release different oligosaccharides. There are indications that pleiotropic plant hormones may actually function by activating the enzymes that release these other, more specific chemical messengers from the cell wall.

Questions 1-7 refer to the passage above.

1. According to the passage, the five well-known plant hormones are not useful in controlling the growth of crops because

(A) it is not known exactly what functions the hormones perform.

(B) each hormone has various effects on plants.

(D) each hormone has different effects on different kinds of plants.

(E) each hormone works on only a small subset of a cell’s genes at any particular time.

2. The passage suggests that the place of hypothalamic hormones in the hormonal hierarchies of animals is similar to the place of which of the following in plants?

(A) Plant cell walls.

(B) The complement of genes in each plant cell.

(D) The five major hormones.

(E) The oligosaccharides.

3. The passage suggests that which of the following is a function likely to be performed by an oligosaccharide?

(A) To stimulate a particular plant cell to become part of a plant’s mot system.

(B) To stimulate the walls of a particular cell to produce other oligosaccharides.

(D) To duplicate the gene complement in a particular plant cell.

(E) To produce multiple effects on a particular subsystem of plant cells.

4. The author mentions specific effects that auxin has on plant development in order to illustrate the

(A) point that some of the effects of plant hormones can be harmful.

(B) way in which hormones are produced by plants.

(D) differences among the best-known plant hormones.

(E) concept of pleiotropy as it is exhibited by plant hormones.

5. According to the passage, which of the following best describes a function performed by oligosaccharides?

(A) Regulating the daily functioning of a plant’s cells.

(B) Interacting with one another to produce different chemicals.

(D) Producing the hormones that cause plant cells to differentiate to perform different functions.

(E) Influencing the development of a plant’s cells by controlling the expression of the cells’ genes.

6. The passage suggests that, unlike the pleiotropic hormones, oligosaccharides could be used effectively to

(A) trace the passage of chemicals through the walls of cells.

(B) pinpoint functions of other plant hormones.

(D) alter the complement of genes in the cells of plants.

(E) alter the effects of the five major hormones on plant development.

7. The author discusses animal hormones primarily in order to

(A) introduce the idea of a hierarchy of hormones.

(B) explain the effects that auxin has on plant cells.

(D) illustrate the way in which particular hormones affect animals.

(E) explain the distinction between hormones and regulatory molecules.

「词汇装备」

subset n. 子集；子设备；小团体

regulatory adj. 管理的；控制的；调整的

pleiotropic adj. 多效性的；多向性的

vascular adj. 血管的

be analogous to与…类比；与…类似

anterior adj. 前面的；先前的

答案详解

1.B 解析细节题。第二段第二句中提到：The five has so many simultaneous effects that they are not very useful in artificially controlling the growth of crops，故本题应选B项。

2.D 解析通过第三段的叙述可知：下丘脑决定了后面一系列荷尔蒙的释放，它是这个等级体质中最高的，最后一段中提到：多向性荷尔蒙激发酶释放其他的专一化学传送物质，故可以推测与下丘脑等级类似的是多向性荷尔蒙，即前文提到的物种主要荷尔蒙，故选D项。

3.A 解析推断题。第一段中提到：Studies of plants have now identified a new class of regulatory molecules called oligosaccharide，前面又提到调控分子和荷尔蒙是用来控制特定细胞中的一小部分基因的表达的，故本题应选A项。

4.E 解析推断题。作者在提及生长素之前，提到：Unlike the oligosaccharide, the five well-known plant hormones are pleiotropic rather than specific, that is, each has more than one effect on the growth and development of plants，然后作者以auxin为例对这个观点进行了证明，故本题应选E项。

5.E 解析细节题。文章第一段提到：低聚糖是用来控制特定细胞中的一小部分基因的表达的，故E项是正确的。

6.C 解析推断题。文章第二段提到：The five has so many simultaneous effects that they are not very useful in artificially controlling the growth of crops，之前作者还提到低聚糖和这五种多向性荷尔蒙是不同的，故本题应选C项。

7.A 解析文章第三段作者提到动物荷尔蒙，并得出结论：there is a hierarchy of hormones，之后作者提到：Such a hierarchy may also exist in plants，所以可以推测作者提到动物荷尔蒙是为了引出荷尔蒙等级这一概念，故本题应选A项。

◆Passage 10　　　　　　　　　　　　文章结构：观点对比型

It was once believed that the brain was independent of metabolic processes occurring elsewhere in the body. In recent studies, however, we have discovered that the production and release in brain neurons of the neurotransmitter serotonin (neurotransmitters are compounds that neurons use to transmit signals to other cells) depend directly on the food that the body processes.

Our first studies sought to determine whether the increase in serotonin observed in rats given a large injection of the amino acid tryptophan might also occur after rats ate meals that change tryptophan levels in the blood. We found that, immediately after the rats began to eat, parallel elevations occurred in blood tryptophan, brain tryptophan, and brain serotonin levels. These findings suggested that the production and release of serotonin in brain neurons were normally coupled with blood-tryp-tophan increases. In later studies we found that injecting insulin into a rat’s bloodstream also caused parallel elevations in blood and brain tryptophan levels and in serotonin levels. We then decided to see whether the secretion of the animal’s own insulin similarly affected serotonin production. We gave the rats a carbohydrate—containing meal that we knew would elicit insulin secretion. As we had hypothesized, the blood tryptophan level and the concentrations of tryptophan serotonin in the brain increased after the meal.

Surprisingly, however, when we added a large amount of protein to the meal, brain tryptophan and serotonin levels fell. Since protein contains tryptophan, why should it depress brain tryptophan levels? The answer lies in the mechanism that provides blood tryptophan to the brain cells. This same mechanism also provides the brain cells with other amino acids found in protein, such as tyrosine and leucine. The consumption of protein increases blood concentration of the other amino acids much more, proportionately, than it does that of tryptophan. The more protein in the meal, the lower is the ratio of the resulting blood-tryptophan concentration to the concentration of competing amino acids, and the more slowly is tryptophan provided to the brain. Thus the more protein in a meal, the less serotonin subsequently produced and released.

Questions 1-9 refer to the passage above.

1. Which of the following titles best summarizes the contents of the passage?

(A) Neurotransmitters: Their Crucial Function in Cellular Communication

(B) Diet and Survival: An Old Relationship Reexamined

(D) Amino Acids and Neurotransmitters：The Connection Between Serotonin Levels and Tyrosine

(E) The Effects of Food Intake on the Production and Release of Serotonin: Some Recent Findings

2. According to the passage, the speed with which tryptophan is provided to the brain cells of a rat varies with the

(A) amount of protein present in a meal.

(B) concentration of serotonin in the brain before a meal.

(D) concentration of tryptophan in the brain before a meal.

(E) number of serotonin-containing neurons present in the brain before a meal.

3. According to the passage, when the authors began their first studies, they were aware that

(A) they would eventually need to design experiments that involved feeding rats high concentrations of protein.

(B) tryptophan levels in the blood were difficult to monitor with accuracy.

(D) there were many neurotransmitters whose production was dependent on metabolic processes elsewhere in the body.

(E) serotonin levels increased after rats were injected with a large amount of tryptophan.

4. According to the passage, one reason that the authors gave rats carbohydrates was to

(A) depress the rats’ tryptophan levels.

(B) prevent the rats from contracting diseases.

(D) demonstrate that insulin is the most important substance secreted by the body.

(E) compare the effect of carbohydrates with the effect of proteins.

5. According to the passage, the more protein a rat consumes, the lower will be the

(A) ratio of the rat’s blood-tryptophan concentration to the amount of serotonin produced and released in the rat’s brain.

(B) ratio of the rat’s blood-tryptophan concentration to the concentration in its blood of the other amino acids contained in the protein.

(D) number of neurotransmitters of any kind that the rat will produce and release.

(E) number of amino acids the rat’s blood will contain.

6. The authors’ discussion of the “mechanism that provides blood tryptophan to the brain cells” (para. 3) is meant to

(A) stimulate further research studies.　

(B) summarize an area of scientific investigation.

(D) provide supporting evidence for a controversial scientific theory.

(E) refute the conclusions of a previously mentioned research study.

7. According to the passage, an injection of insulin was most similar in its effect on rats to an injection of　

(A) tyrosine.

(B) leucine.　

(D) tryptophan.

(E) protein.

8. It can be inferred from the passage that which of the following would be LEAST likely to be a potential source of aid to a patient who was not adequately producing and releasing serotonin?

(A) Meals consisting almost exclusively of protein.

(B) Meals consisting almost exclusively of carbohydrates.

(D) Meals that had very low concentrations of tyrosine.

(E) Meals that had very low concentrations of leucine.

9. It can be inferred from the passage that the authors initially held which of the following hypotheses about what would happen when they fed large amounts of protein to rats?

(A) The rats’ brain serotonin levels would not decrease.

(B) The rats’ brain tryptophan levels would decrease.

(D) The rats would produce more insulin.

(E) The rats would produce neurotransmitters other than serotonin.

「词汇装备」

metabolic adj. 变化的；新陈代谢的

neuron n. 神经元，神经单位

bloodstream n. 血流，血液的流动

elicit v. 引出；引起

hypothesize v. 假设，假定

proportionately adv. 相称地，成比例地

secretion n. 分泌；分泌物；藏匿

答案详解

1.E 解析主旨题。第一段第二句叙述了本文的主题：the production and release in brain neurons of the neurotransmitter serotonin…depend directly on the food that the body processes，所以可知E项是正确的。

2.A 解析推断题。全文倒数第二句提到：食物中蛋白质越多，最终血中色氨酸和其他氨基酸的比就越低，从而向脑中提供色氨酸也就越慢，所以食物中蛋白质的含量和色氨酸供给到鼠类的神经细胞的速度有关，故A项是正确的。

3.E 解析第二段第一句中提到：我们最初的研究试图确定，给老鼠注射色氨酸会引起血清素升高的现象，在给老鼠喂能改变色氨酸含量的食物后是否会发生，所以可知在作者最开始研究时，他们已经发现给老鼠注射色氨酸会引起血清素升高，故E项是正确的。

4.C 解析推断题。文章第二段倒数第三句中提到：为了观察动物自身的胰岛素分泌是否同样影响了血清素生成，所以作者喂老鼠能促进胰岛素合成的含碳水化合物食物，故C项是正确的。

5.B 解析细节题。文章倒数第二句中提到：食物中蛋白质越多，最终血中色氨酸和其他氨基酸的比就越低，故B项是正确的。

6.C 解析第三段第一句中作者提出了一个特殊的现象，即当我们给食物中添加大量蛋白质后，脑中色氨酸和血清素含量反而下降，然后作者提到产生这种现象的原因是色氨酸进入脑细胞的机制，所以可知作者讨论色氨酸进入脑细胞的机制是为了解释某一特殊的观测结果故本题应选C项。

7.D 解析推断题。第二段中作者提到胰岛素和色氨酸都可以侧近血清素的分泌，所以可知给老鼠打一针胰岛素，相当于给它打一针色氨酸，故本题应选D项。

8.A 解析推断题。文章最后一句提到：蛋白质含量越高，血清素分泌得越少，所以吃只含蛋白质的食物最不能帮助病人有效的分泌血清素，故本题应选A项。

9.A 解析推断题。根据第三段首句“Surprisingly…when we added a large amount of protein to the meal, brain tryptophan and serotonin levels fell”可知，当给老鼠喂大量蛋白质后老鼠脑中血清素含量下降的结果很出乎意料，所以可以推断作者预想给老鼠喂大量蛋白质后老鼠脑中血清素含量不会下降，所以A项是正确的。

◆Passage 11　　　　　　　　　　　　文章结构：观点对比型

According to a recent theory, Archeanage gold-quartz vein systems were formed over two billion years ago from magmatic fluids that originated from molten granite-like bodies deep beneath the surface of the Earth. This theory is contrary to the widely held view that the systems were deposited from metamorphic fluids, that is, from fluids that formed during the dehydration of wet sedimentary rocks. The recently developed theory has considerable practical importance. Most of the gold deposits discovered during the original gold rushes were exposed at the Earth’s surface and were found because they had shed trails of alluvial gold that were easily traced by simple prospecting methods. Although these same methods still lead to an occasional discovery, most deposits not yet discovered have gone undetected because they are buried and have no surface expression.

The challenge in exploration is therefore to unravel the subsurface geology of an area and pinpoint the position of buried minerals. Methods widely used today include analysis of aerial images that yield a broad geological overview; geophysical techniques that provide data on the magnetic, electrical, and mineralogical properties of the rocks being investigated; and sensitive chemical tests that are able to detect the subtle chemical halos that often envelop mineralization. However, none of these high-technology methods are of any value if the sites to which they are applied have never mineralized, and to maximize the chances of discovery the explorer must therefore pay particular attention to selecting the ground formations most likely to be mineralized. Such ground selection relies to varying degrees on conceptual models, which take into account theoretical studies of relevant factors.

These models are constructed primarily from empirical observations of known mineral deposits and from theories of ore-forming processes. The explorer uses the models to identify those geological features that are critical to the formation of the mineralization being modeled, and then tries to select areas for exploration that exhibit as many of the critical features as possible.

Questions 1-8 refer to the passage above.

1. The author is primarily concerned with

(A) advocating a return to an older methodology.

(B) explaining the importance of a recent theory.

(D) describing events leading to a discovery.

(E) challenging the assumptions on which a theory is based.

2. According to the passage, the widely held view of Archeanage gold-quartz vein systems is that such systems

(A) were formed from metamorphic fluids.

(B) originated in molten granite-like bodies.

(D) generally have surface expression. 　

(E) are not discoverable through chemical tests.

3. The passage implies that which of the following steps would be the first performed by explorers who wish to maximize their chances of discovering gold?

(A) Surveying several sites known to have been formed more than two billion years ago.

(B) Limiting exploration to sites known to have been formed from metamorphic fluid.

(D) Using geophysical methods to analyze rocks over a broad area.

(E) Limiting exploration to sites where alluvial gold has previously been found.

4. Which of the following statements about discoveries of gold deposits is supported by information in the passage?

(A) The number of gold discoveries made annually has increased between the time of the original gold rushes and the present.

(B) New discoveries of gold deposits are likely to be the result of exploration techniques designed to locate buried mineralization.

(C) It is unlikely that newly discovered gold deposits will ever yield as much as did those deposits discovered during the original gold rushes.

(D) Modern explorers are divided on the question of the utility of simple prospecting methods as a source of new discoveries of gold deposits.

(E) Models based on the theory that gold originated from magmatic fluids have already led to new discoveries of gold deposits.

5. It can be inferred from the passage that which of the following is easiest to detect?

(A) A gold-quartz vein system originating in rnagmatic fluids.

(B) A gold-quartz vein system originating in metamorphic fluids.

(D) A gold deposit that has shed alluvial gold.

(E) A gold deposit that exhibits chemical halos.

6. The theory mentioned in line 1 relates to the conceptual models discussed in the passage in which of the following ways?

(A) It may furnish a valid account of ore-forming processes, and, hence, can support conceptual models that have great practical significance.

(B) It suggests that certain geological formations, long believed to be mineralized, are in fact mineralized, thus confirming current conceptual models.

(C) It suggests that there may not be enough similarity across Archeanage gold-quartz vein systems to warrant the formulation of conceptual models.

(D) It corrects existing theories about the chemical halos of gold deposits, and thus provides a basis for correcting current conceptual models.

(E) It suggests that simple prospecting methods still have a higher success rate in the discovery of gold deposit than do more modern methods.

7. According to the passage, methods of exploring for gold that are widely used today are based on which of the following facts?

(A) Most of the Earth’s remaining gold deposits are still molten.

(B) Most of the Earth’s remaining gold deposits are exposed at the surface.

(D) Only one type of gold deposit warrants exploration, since the other types of gold deposits are found in regions difficult to reach.

(E) Only one type of gold deposit warrants exploration, since the other types of gold deposits are unlikely to yield concentrated quantities of gold.

8. It can be inferred from the passage that the efficiency of model-based gold exploration depends on which of the following?

Ⅰ. The closeness of the match between the geological features identified by the model as critical and the actual geological features of a given area.

Ⅱ. The degree to which the model chosen relies on empirical observation of known mineral deposits rather than on theories of ore-forming processes.　

Ⅲ. The degree to which the model chosen is based on an accurate description of the events leading to mineralization. 　

(A) Ⅰ only

(B) Ⅱ only

(D) Ⅰ and Ⅲ only　

(E) Ⅰ, Ⅱ and Ⅲ

「词汇装备」

vein n. 血管；叶脉；岩脉

magmatic adj. 岩浆的

molten adj. 熔化的；铸造的；炽热的

granite n. 花岗岩

metamorphic adj. 变质的；变性的；变态的

dehydration n. 脱水

sedimentary rock沉积岩；水成岩

alluvial adj. 冲积的

unravel v. 解开；阐明；解决

aerial adj. 空中的，航空的；空气的

magnetic adj. 地磁的；有磁性的

mineralogical adj. 矿物学的

halo n. 光环；荣光

答案详解

1.B 解析主旨题。文章首先对一种新的成矿理论进行了介绍，然后探讨了新理论带来的研究方式的变化，故本题应选B项。

2.A 解析细节题。第一段第二句指出古代金矿石系统形成的普遍观点是：the systems were deposited from metamorphic fluids，故本题应选A项。

3.C 解析推断题。根据第二段倒数一、二可知，为了尽可能增加发现机会，探测者必须要特别注意挑选有可能矿化的地层，这种地层选择依赖于设计模型，所以可以推测想要发现金矿，第一步应该用正确的模型来选定继续探测的地点，故本题选C项。

4.B 解析细节题。第二段结尾处提到：to maximize the chances of discovery the explorer must therefore pay particular attention to selecting the ground formations most likely to be mineralized. Such ground selection relies to varying degrees on conceptual models…，故本题应选B项。

5.D 解析推断题。第一段倒数第二句提到：Most of the gold deposits discovered…were exposed at the Earth’s surface…they had shed trails of alluvial gold…，故D项是正确的。

6.A 解析推断题。根据文章第二段内容可知，模型主要包括找矿经验和矿石形成理论，所以可知第一行中提到的理论提供了矿石形成机制的有力解释，所以可以支持这一模型，故本题应选A项。

7.C 解析推断题。第一段结尾处提到：大部分未被发现的矿由于深埋地下，没有地表特征而无法探测，所以本题应选C项。

8.D 解析文章最后一段提到：探测者用此模型去确定对被作为模型的矿化形成有决定作用的地理因素，然后，试图为探测挑选出尽可能多的显示出决定因素的地区，所以Ⅰ项是正确的；根据第二段内容可知Ⅲ项也是正确的，故本题选D项。

◆Passage 12 　　　　　　　　　　　文章结构：结论说明型

Coral reefs are one of the most fragile, biologically complex, and diverse marine ecosystem on Earth. This ecosystem is one of the fascinating paradoxes of the biosphere: how do clear, and thus nutrient-poor waters support such prolific and productive communities? Part of the answer lies within the tissues of the corals themselves. Symbiotic cells of algae known as zooxanthelae carry out photosynthesis using the metabolic wastes of the coral thereby producing food for themselves, for their corals, hosts, and even for other members of the reef community. This symbiotic process allows organisms in the reef community to use sparse nutrient resources efficiently.

Unfortunately for coral reefs, however, a variety of human activities are causing worldwide degradation of shallow marine habitats by adding nutrients to the water. Agriculture, slash-and-bum land clearing, sewage disposal and manufacturing that creates waste by-products all increase nutrient loads in these waters. Typical symptoms of reef decline are destabilized herbivore populations and an increasing abundance of algae and filter-feeding animals. Declines in reef communities are consistent with observations that nutrient input is increasing in direct proportion to growing human populations, thereby threatening reef communities sensitive to subtle changes in nutrient input to their waters.

Questions 1-5 refer to the passage above.

1. The passage is primarily concerned with

(A) describing the effects of human activities on algae in coral reefs.

(B) explaining how human activities are posing a threat to coral reef communities.

(D) explaining how coral reefs produce food for themselves.

(E) describing the abundance of algae and filter-feeding animals in coral reef areas.

2. The passage suggests which of the following about coral reef communities?

(A) Coral reef communities may actually be more likely to thrive in waters that are relatively low in nutrients.

(B) The nutrients on which coral reef communities thrive are only found in shallow waters.

(D) The growth of coral reef communities tends to destabilize underwater herbivore populations.

(E) Coral reef communities are more complex and diverse than most ecosystems located on dry land.

3. The author refers to “filter-feeding animals” in para. 2 in order to

(A) provide an example of a characteristic sign of reef deterioration.

(B) explain how reef communities acquire sustenance for survival.

(D) indicate a cause of decreasing nutrient input in waters that reefs inhabit.

(E) identify members of coral reef communities that rely on coral reefs for nutrients.

4. According to the passage, which of the following is a factor that is threatening the survival of coral reef communities?

(A) The waters they inhabit contain few nutrient resources.

(B) A decline in nutrient input is disrupting their symbiotic relationship with zooxanthellae.

(D) They are too biologically complex tc survive in habitats with minimal nutrient input.

(E) Waste by-products result in an increase in nutrient input to reef communities.

5. It can be inferred from the passage that the author describes coral reef communities as paradoxical most likely for which of the following reasons？

(A) They are thriving even though human activities have depleted the nutrients in their environment.

(B) They are able to survive in spite of an over-abundance of algae inhabiting their waters.

(D) Their metabolic wastes contribute to the degradation of the waters that they inhabit.

(E) They are declining even when the water surrounding them remains clear.

「词汇装备」

fragile adj. 脆弱的；脆的；易碎的

paradox n. 悖论；自相矛盾的人或事

biosphere n. 生物圈

prolific adj. 多产的；丰富的

algae n. 藻类；海藻

photosynthesis n. 光合作用

sparse adj. 稀疏的；稀少的

destabilized adj. 非稳定的

herbivore n. 食草动物

filter-feeding滤食

答案详解

1.B 解析主旨题。文章首先对于珊瑚礁的生存方式进行了介绍，然后以此为基础说明人类的活动是如何对珊瑚礁造成影响的，故本题应选B项。

2.A 解析推断题。文章最后一句中指出：富营养化的水体使得珊瑚礁不宜生存，所以可以推测珊瑚礁群落在营养水平低的水体中更易生存，故本题选A项。

3.A 解析推断题。这句话的意思是：珊瑚礁减少的典型表现是：植食性物种下降，藻类、过滤性捕食的动物(如贝类)增多，所以可以推测作者提到“过滤性捕食动物”是为了举例说明珊瑚礁的衰退，故本题选择A项。

4.E 解析第二段第二句提出：农业、过度砍伐、污水排放以及产生大量废物的制造业都加剧了水体的富营养化，而在富营养化的水体中珊瑚礁无法生存，故本题选E项。

5.C 解析推断题。第一段第二句中提到：clear, and thus nutrient-poor waters support such prolific and productive communities，即贫营养水体支撑了大量的生物群落，故作者说珊瑚礁群落“看似矛盾”因为他们能在食物有限的环境下生存，故本题选C项。

◆Passage 13 　　　　　　　　　　　文章结构：结论说明型

Since the 1994 introduction to supermarket shelves of Calgene’s Flaw Savr tomato, the first genetically modified food item to be offered to consumers, transgenic foods have made a quiet transformation of the food production system in America. The amount of farmland planted with transgenic crops exploded from barely over 10,000 acres in 1994 to approximately 200 million acres in 2004. The Grocery Manufacturers of America estimate that transgenic crops—primarily corn and soybeans—now appear in approximately 75 percent of all processed foods found in grocery stores. While many in the industry applaud this transformation as a beneficial use of technology that will improve products and profits, many observers are concerned that the long-term effects of these transgenic foods are still poorly understood.

Humans have been modifying food since the dawn of agriculture. The difference between conventional selective breeding and biotechnology is that instead of relying on natural but targeted reproductive processes, biotechnology relies on the tools of recombinant DNA technology, primarily restriction endonucleases and ligase enzymes, to alter the genetic codes of organisms in ways that could not occur in nature. One transgenic food organism, the “Bt potato,” combines the genetic code of a regular potato with that of the Bacillus thuringiensis bacterium, resulting in a potato that is poisonous to many types of insect pests, but still edible by humans.

Critics of bioengineering warn that we have no long-term studies on the effects of such manipulation of food organisms. Modified foods might have unintended consequences for the health of people who eat them. The modifications introduced into domesticated crops might spread into wild plant species, fundamentally altering the ecosystem. Many critics have argued that the introduction of bioengineered foods gives biotechnology companies undue power over the processes of food production, and thereby leaves small farmers and farmers in the developing world at the mercy of large corporations. Perhaps the most common criticism leveled at transgenic foods is that they are “not natural.”

Despite these criticisms, the agricultural industry in America has continued to move ahead with further research into and planting of transgenic crops. Government regulatory agencies, such as the EPA, the FDA, and the Department of Agriculture, have essentially given biotechnology companies free rein as long as they can establish that transgenic crops are “substantially similar” to conventional crops, and biotechnology companies have so far successfully fought off all efforts to have transgenic foods labeled as such. To date, no confirmed case of harmful health effects from transgenic foods has been documented. American consumers, although they consistently voice doubts about transgenic foods when asked about them on surveys, are apparently unconcerned that they eat, on average, several genetically modified foods each week.

Questions 1-6 refer to the passage above.

1. Which of the following statements best summarizes the main idea of the passage?

(A) The tools of recombinant DNA technology have spurred a fundamental transformation in the way in which food is engineered and grown.

(B) A majority of Americans now eat transgenic foods because of the benefits in nutrition and cost offered by these new products.

(C) Despite the fact that transgenic foods have been proven unsafe for human consumption, biotechnology companies have quitly achieved widespread distribution of these foods.

(D) Genetically modified foods, although they face criticism from those who doubt their safety, have become a significant part of the American food production system.

(E) Biotechnology offers a solution to the growing levels of hunger and malnutrition in the developing world, although critics worry that transgenic foods may have unintended health consequences.

2. The passage mentions each of the following as concerns raised by critics of transgenic foods EXCEPT:

(A) Transgenic foods might affect the health of consumers in unforeseen ways.

(B) Transgenic foods may be more resistant to insect pests than conventional crops.

(C) An agricultural distribution system based on genetically modified food will leave small farmers dependent on biotechnology conglomerates.

(D) There is no data on what the health effects may be for humans who eat transgenic foods over a period of several decades.

(E) Plant species in the wild might become contaminated by genetically modified species.

3. Which of the following inferences drawn from the statements in the final paragraph, if accurate, might best explain the apparently contradictory finding that Americans voice concerns over transgenic foods in polls but consume these foods on a regular basis?

(A) Government regulatory agencies have approved the sale of transgenic foods to consumers as long as the producers can establish that the transgenic foods are “substantially similar” to conventional foods.

(B) American farmers planted over 200 million acres with transgenic crops in 2004, a substantial increase from the acreage planted with transgenic crops a decade earlier.

(C) American consumers may be unaware that they are eating transgenic foods because of the biotechnology industry’s success in preventing the labeling of these foods.

(D) Critics of genetic engineering have been unsuccessful in their attempts to impose bans on transgenic food through the EPA and FDA.

(E) As of the writing of the passage, no deaths or other adverse health effects had been documented in connection with the consumption of transgenic foods.

4. The relationship between a conventional potato and a “Bt potato” is most similar to which of the following?

(A) The relationship between a conventional automobile and one that has been equipped with a revolutionary new engine technology that allows it to fly.

(B) The relationship between a regular hamburger and one that has been made poisonous through the addition of bleach.

(C) The relationship between a laptop computer and a similar computer that is twice as fast as the first computer because it has a more powerful central processing unit.

(D) A wild chicken and a domesticated chicken that has been bred to gain weight three times faster than a wild chicken.

(E) A boiled potato and a baked potato with all the fixings.

5. The second paragraph plays what role in the passage?

(A) It presents the first of two arguments discussed in the passage.

(B) It suggests that the hypothesis advanced in the first paragraph is incomplete.

(D) It suggests any way of looking at a topic that differs from the conventional view presented in the first paragraph.

(E) It provides background information relevant to the topic discussed in the following paragraphs.

6. The author’s attitude toward transgenic food can best be described as which of the following?

(A) Angry and concerned.

(B) Accepting and optimistic.

(D) Interested but uncommitted.　

(E) Hopeful but suspicious.

「词汇装备」

genetically modified food转基因食品

transgenic adj. 转基因的；基因改造的

applaud v. 赞同；称赞；向…喝彩

recombinant n. 重组；重组体

manipulation n. 操作；操纵；控制

level...at（用枪）对准；将…的矛头指向

rein n. 缰绳；驾驭；统治；支配

答案详解

1.D 解析主旨题。第一段最后一句中作者叙述了本文的主题，即“While many in the industry applaud this transformation as a beneficial use of technology that will improve products and profits, many observers are concerned that the long-term effects of these transgenic foods are still poorly understood.”，故本题选D项。

2.B 解析细节题。文章第三段中列举了对于转基因食物的负面观点，其中不包含B项，故本题选B项。

3.C 解析推断题。最后一段倒数第二句提到“biotechnology companies have so far successfully fought off all efforts to have transgenic foods labeled as such”，最后一句中作者又说道很多美国人不知道自己每天吃的很多食物都是转基因作物，故本题选C项。

4.A 解析第二段最后一句中提到了普通土豆和“Bt potato”的关系，即“the “Bt potato,” combines the genetic code of a regular potato with that of the Bacillus thuringiensis bacterium”，故A项描述的关系与文章中提到的土豆和“Bt potato”的关系相似，故本题选A项。

5.E 解析第二段介绍了转基因食物与传统食物的不同之处，为文章的主题内容提供背景知识，故本题选E项。

6.D 解析态度题。文章中作者叙述了转基因食物的相关知识，提到了大家对其的批评及其发展，语气中立，全文旨在陈述事实，故D项最合适。

◆Passage 14 　　　　　　　　　　　文章结构：现象解释型

Iguacu Falls, which sit on the border between Argentina and Brazil, are said to make Niagara look like a leaky faucet. The great cataracts stretch for two and a half miles across lushly foliaged rocky outcroppings before plunging a staggering two hundred and thirty feet into the river below.

The falls region is densely forested, and is home to a wide variety of plants and animals, including a number of endangered ones. It is a paradise where parrots live and swoop through the spray butterflies cavort among the tropical plants and coatis, and giant otters and anteaters amble through the trees. The foliage itself varies between tropical and deciduous with orchids blushing in the shade of pines and ferns nodding gracefully in the shadow of fruit trees.

Depending on rainfall and water flow, between 200 and 300 individual falls tumble over the cliffs creating a stunning panoply of churning water. Small wonder that this natural powerhouse attracted the attention of developers. At the top of the falls on the Parana River sits Italpu Dam, the world’s largest operational hydroelectric power plant. The dam is often numbered among the wonders of the modern world.

The falls’ superlatives don’t stop with technology. Many consider the cataract system itself one of the natural wonders of the world. In 1986, UNESCO (United Nations Educational, Scientific, and Cultural Organization) concurred when it declared the falls a World Heritage site in order to ensure its preservation in the face of continuing technological development.

Questions 1-4 refer to the passage above.

1. The comparison in the first sentence is meant to emphasize the

(A) Abundant beauty of Niagara Falls.

(B) Plumbing problems that can be caused by building in close proximity to a waterfall.

(D) Distance of Iguacu Falls from civilization.

(E) Fact that Niagara Falls is a less popular tourist destination than Ignacu Falls.

2.The author’s attitude toward Iguaqu Falls can best be described as which of the following?

(A) Overweening pride.

(B) Positive appreciation.

(D) Apathetic objectivity.

(E) Cautious optimism.

3. What can most reasonably be inferred from the information in the final two paragraphs?

(A) Iguaqu Falls’ success as a hydroelectric site could potentially cause a threat to its longevity.

(B) Conservationist efforts have made a tremendous impact in the maintenance of the Itaipu Dam hydroelectric power plant.

(D) UNESCO considers the preservation of Iguaqu Falls crucial to the balance of the world ecosystem.

(E) Developers consider any opportunity to invest in hydroelectric power a lucrative business venture.

4. The author of the passage is primarily concerned with

(A) Exalting the beauties of a variety of waterfall sites.

(B) Outlining the history of Iguaqu Falls since its discovery.

(D) Describing Iguaeu Falls in terms that would make sense to an American audience.

(E) Discussing the tension between economic development and natural conservation.

「词汇装备」

leaky adj. 漏的；有漏洞的

faucet n. 水龙头

cataract n. 大瀑布；洪水；白内障

lushly adv. 多青草地；繁荣地

outcropping n. 出露地表；露出；露头

staggering adj. 令人惊愕的；蹒跚的；犹豫的

cavort v. 腾跃；欢跃

otter n. 水獭；水獭皮

anteater n. 食蚁兽

amble v. （马）缓行；从容漫步

foliage n. 植物；叶子（总称）

deciduous adj. 落叶性的，脱落性的

hydroelectric adj. 水力发电的；水电治疗的

concur v. 同意；一致；互助

答案详解

1.C 解析推断题。文章首句提到：伊古阿斯瀑布坐落于阿根廷和巴西的交界处，比起伊古阿斯瀑布，尼亚拉加瀑布就像是一个漏水的水龙头，这句话突出了伊古阿斯瀑布的宏大，进而说明尼亚拉加瀑布的渺小，故本题选C项。

2.B 解析态度题。作者在文中对于伊古阿斯瀑布的美景及其周边的丰富的生态系统进行了描述，可见作者对其的赞扬，故本题选B项。

3.A 解析推断题。文章最后一句中提到：In 1986, UNESCO concurred when it declared the falls a World Heritage site in order to ensure its preservation in the face of continuing technological development，由此可以推断伊古阿斯瀑布可能会由于电站的建立遭到破坏，故本题选A项。

4.C 解析主旨题。文章主要对伊古阿斯瀑布进行了描述，并叙述了其经济价值，故本题选C项。