prep 1-3,NN进

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.

我实在不清楚E的答案是怎么支持的，请帮下忙，感谢了阿

。。。再看了下题目的结论：  The seasonal variation in group size can probably be explained by a seasonal variation in mortality among young voles.    group size 的seasonal variation 和young voles的死亡率由关系。。。

其它答案根本没有涉及到young vole， 只有e 对。。。

本题前面说了一大堆天气的东西，是希望把我们的思想往天气那方面带。。。然后调进陷阱。。。。