求助prep1-3

wjfruc

3.    (24275-!-item-!-188;#058&000768)

 

The prairie vole, a small North American grassland rodent, breeds year-round, and a group of voles living together consists primarily of an extended family, often including two or more litters.  Voles commonly live in large groups from late autumn through winter; from spring through early autumn, however, most voles live in far smaller groups.  The seasonal variation in group size can probably be explained by a seasonal variation in mortality among young voles.

 

Which of the following, if true, provides the strongest support for the explanation offered?

 

(A) It is in the spring and early summer that prairie vole communities generally contain the highest proportion of young voles.

(B) Prairie vole populations vary dramatically in size from year to year.

(C) The prairie vole subsists primarily on broad-leaved plants that are abundant only in spring.

(D) Winters in the prairie voles' habitat are often harsh, with temperatures that drop well below freezing.

(E) Snakes, a major predator of young prairie voles, are active only from spring through early autumn.

A为什么不对啊？为什么选E啊？

 

wjfruc

自己顶一下

羽痕

你的想法肯定是因为spring和early summer幼崽多，所以死亡率高，但A是讲那时活着的幼崽有很多，况且A只是讲了spring和early summer,而题中是spring to autumn,所以不好。

E无懈可击，spring to autumn 幼崽的捕食者蛇很活跃，吃掉prairie vole

popris

同意楼上,而且A是无关选项,陈述spring和early summer幼崽多与题目的结论死亡率没有联系.

imharper

a seasonal variation in mortality among young voles.

要和这个有关

JamesYi

A 不能提供支持，因为幼崽比例的多少，并不能推出幼崽的数量有任何变化----例如：如果有一种专门捕食成年vole的蛇，而这种蛇在春季到秋季很活跃，在其它时间不活跃，那么也会产生上述的现象，但是幼崽vole的数量却不需要有任何变化。

wjfruc

I am clear now. Thank you all