Passage 3

Choose the best answer and complete the passage.（选择最恰当的选项完成短文）（12分）

Number sense（感觉）is not the ability to count.It is the ability to recognize（认出） a change in number. Human beings are born with this ability. Surprisingly, 1 show that many animals are,too.For example,many birds have good number sense.If a nest（巢）has four eggs and you remove one, the bird will not notice. However, if you remove two, the bird generally leaves. This means that the bird 2 the difference between two and three.

Another interesting test showed a bird's 3 number sense. A man was trying to take a photo of a crow that had a nest in a tower（塔）,but the crow always left when she saw him coming. The bird did not 4 until the man left the tower. The man had an idea. He took another man with him to the tower. One man left and the other stayed, but they weren't successful in fooling the bird. The crow stayed away until the second man left, too. The test was 5 with three men and then with four men. It was not until five men went into the tower and only four left that they finally managed to take a photo.

How good is a human's number sense? It's not very good. For example, babies about fourteen months old 6 notice if something is taken away from a small group. But when the number goes beyond three or four,the children are often very confused（迷惑的）.

It seems that number sense is something we have in common with many animals in this world, and that our human ability is not much better than a crow's.

（　） 1. A. ideas B. plans C. experiments D. books

（　） 2. A. went out B. found out C. looked out D. turned out

（　） 3. A. forgetful B. friendly C. amazing D. silly

（　） 4. A. leave B. return C. fly D. sing

（　） 5. A. repeated B. stopped C. noticed D. produced

（　） 6. A. never B. rarely C. hardly D. usually