Number sense is not the ability to count. It is the ability to recognize a __16__ in number. Human beings are born with this ability. __17__, 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 __18__. However, if you remove two, the bird __19__ leaves. This means that the bird knows the __20__ between two and three.
Another interesting experiment showed a bird's __21__ number sense. A man was trying to take a photo of a crow that had a nest in a tower, but the crow always left when she saw him coming. The bird did not _22__ until the man left the tower. The man had an __23__. He took another man with him to the tower. One man left and the other stayed, but they did not __24__ the bird. The crow stayed away until the second man left, too. The experiment was __25__ with three men and then with four men. But the crow did not return to the nest until all the men were __26__. It was not until five men went into the tower and only four left that they were __27__ 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 __28_ group. But when the number goes beyond three or four, the children are __29__ fooled.
It seems that number sense is something we have in common with many animals in this world, and that our human __30__ is not much better than a crow's.
空白处选择
考查动词词义辨析。根据上文第一句的“recognize”和下文的“knows the ”语义提示可知，这是这二个词的同义词复现，本句句义为：如果一个鸟窝里有四颗鸟蛋，你拿走一个，鸟儿就会发现。A“生存下来”，B“关心”，C“孵（蛋）”均不符合语境。故选D。
我国保护少年儿童权益的专项法律是《中华人民共和国未成年人保护法》。（ ）
MP3（ ）。
计算机软件是指（ ）。
下面哪一项不属于维护交易安全原则的内容？（ ）
围绕《建国以来的重大科技成就》一课，做一个教案。
请围绕“城乡发展一体化”写一篇小论文，题目自拟，角度不限，要求：结构完善、条理清晰、有说服力。
在国际关系中，第三世界国家历来是中国团结合作的对象，因为 ①第三世界国家是国际社会一支重要的政治力量 ②团结第三世界国家符合中国的国家利益 ③合作是第三世界国家共同发展的必由之路 ④第三世界国家在南北关系中处于主导地位（ ）
微观经济学要解决的问题是（ ）
机关文书部门或业务部门在年终或第二年上半年对归卷的文件材料进行整理等工作，称为（ ）。
20世纪70年代中国外交有了重大突破和转机，转变的关键是（ ）
