I单元广东
I1 完形填空
I1 [2013·广东卷]
阅读下面短文，掌握其大意，然后从1～15各题所给的A、B、C和D项中，选出最佳选项。
Number sense is not the ability to count. It is the ability to recognize a __1__ in number. Human beings are born with this ability. __2__，experiments show that many animals are, too. For example, many birds have good number sense. If a nest has four eggs and you remove one, the bird will not __3__．However, if you remove two, the bird __4__ leaves. This means that the bird knows the __5__ between two and three.
Another interesting experiment showed a bird's __6__ number sense. A man was trying to take a photo of a crow(乌鸦)that had a nest in a tower, but the crow always left when she saw him coming. The bird did not __7__ until the man left the tower. The man had an __8__．He took another man with him to the tower. One man left and the other stayed, but they did not __9__ the bird. The crow stayed away until the second man left, too. The experiment was __10__ with three men and then with four men. But the crow did not return to the nest until all the men were __11__．It was not until five men went into the tower and only four left that they were __12__ able to fool the crow.
How good is a human's number sense? It's not very good. For example, babies about fourteen months old almost always notice if something is taken away from a __13__ group. But when the number goes beyond three or four, the children are __14__ fooled.
It seems that number sense is something we have in common with many animals in this world，and that our human __15__ is not much better than a crow's.
1．A. rise B. pattern
C. change D. trend
2．A. Importantly B．Surprisingly
