PREP中的一道!谢谢!

lyq2010200118

The prairie vole, a small NorthAmerican grassland rodent, breeds year-round, and a group of voles livingtogether consists primarily of an extended family, often including two or morelitters.  Voles commonly live in largegroups 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 aseasonal 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 earlysummer that prairie vole communities generally contain the highest proportionof young voles.

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

(C) The prairie vole subsistsprimarily 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 ofyoung prairie voles, are active only from spring through early autumn.

我看过旧帖，明白为什么E对，但是我不明为什么A不对，A也是说young voles的呀~我一开始做的时候就在A和E中纠结。快来个人帮帮我把~~

IBiturbo

好几个单词不认识。。。 查完单词后了解了， 结论是group size 的季节性变化是由young voles的季节性死亡率来决定的，那么要加强…… A， 在春天和早夏，young voles 的比例在group中最高，所以死亡率很低，而前提是from spring through early autumn,however, most voles live in far smaller groups.，是矛盾的，因此不能加强呀！而E， 蛇的出现，from spring through early autumn，肯定会加大voles的死亡率，那么肯定会导致smaller group，与原文前提也相符，是加强的！