单选题 The ostrich, the largest bird in the world at present, lives in the drier regions of Africa outside the actual deserts. Because of its very long, powerful legs and the floating effect of its extended wings, it is able to run at great speed over considerable distances.
The female ostrich normally produces about twenty eggs every rainy season. When the female ostrich begins to lay her eggs, however, she does not begin in her own nest. Instead she goes off in search of the nests of neighboring females and lays two or three eggs in each of them. By the time she has laid eight or nine eggs, she returns and lays the rest in her own nest.
Because of the size of the eggs, the female ostrich cannot lay more than one every two days, so it takes her three weeks to finish laying in her own nest. During that period, she spends a lot of time away from her nest looking for food. And while she is off her nest, other females visit it to lay their eggs amongst hers. By the time she is ready to sit on the eggs to hatch them, there could be up to thirty eggs in her nest, over half of which are not her own.
The female ostrich can comfortably cover only about twenty eggs when she is sitting on the nest, so before settling down she pushes the surplus ten or so eggs out of the nest. The rejected eggs, however, never include any of her own. Each female is remarkably consistent in the size and shape of the eggs she produces, so it is not difficult for her to distinguish her own from those of strangers.
Of all the eggs laid by a colony of ostriches, only a very small number hatch into young birds. There are times when nests are left unprotected, for there are too few males to sit on all the nests at night. Thus there are ample opportunities for their natural enemies to raid the nests and eat the eggs. In fact, nearly 80% of the nests are destroyed. But even if a particular female's nest suffers this fate, there is a good chance that one or two of her eggs will be hatched in the nest of one of her neighbors.

单选题 We learn from the text that an ostrich can go a long distance at high speed as ______.

【正确答案】 C

【答案解析】细节题。短文第一段最后一句指出：Because of its very long，powerful legs and the floating effect of its extended wings...(由于其修长、有力的双腿和其羽翼张开而产生的浮力作用……)，这正是鸵鸟可以快速奔跑很长距离的原因。题干和选项[C]只是将该句的语序做了变换，将because改成了as而已。

单选题 Normally, in every rainy season, the female ostrich produces about ______.

【正确答案】 A

【答案解析】推理判断题。短文第二段第一句指出：The female ostrich normally produces about twenty eggs every rainy season(雌鸵鸟每个雨季通常约产蛋20枚)，而该段最后一句又指出：By the time she has laid eight or nine eggs，she returns...(待产下八九枚蛋后，它便回去，将其他蛋产在自己的巢里)。结合这两处不难推知它产在自己巢里的蛋约12枚，所以本题答案为[A]。虽然计算很简单，但有许多考生误选了[C]项，究其原因，就是没有仔细审题，没有注意到选项中的in her nest这个限定条件所致。

单选题 The female ostrich would push some of the eggs out of her nest because ______.

【正确答案】 D

【答案解析】细节题。本题的答题依据是第四段第一句话：The female ostrich can comfortably cover only about twenty eggs...so before...out of the nest(雌鸵鸟坐在巢中时只能很好地罩住约20枚蛋，所以坐下来孵蛋前它会把多出的十余枚蛋挤出巢去)。其中的only与选项[D]中的a limited number(数量有限)对应。其余各项都属于抓住原文词句进行的发挥。

单选题 The female ostrich identifies her own eggs by their size and ______.

单选题 The female ostrich lays her eggs in her neighbors' nests most probably because ______.

【正确答案】 B

【答案解析】推理判断题。文章最后一段实际上解释了鸵鸟将蛋下在别的巢中的原因。其中最后一句指出：But even if...one or two of her eggs will be hatched in the nest of one of her neighbors(但即便某只雌鸟的巢遭受到了这种噩运，它所下的一两个蛋还是很有可能在邻鸟的巢中孵化出来)。由此即可推知，鸵鸟把蛋下在别的鸟巢中，是因为它无法保护自己所下的每一枚蛋，因此本题答案就是[B]。