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题库 / Prep2007E1-CR-3
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?
It is in the spring and early summer that prairie vole communities generally contain the highest proportion of young voles.
Prairie vole populations vary dramatically in size from year to year.
The prairie vole subsists primarily on broad-leaved plants that are abundant only in spring.
Winters in the prairie voles' habitat are often harsh, with temperatures that drop well below freezing.
Snakes, a major predator of young prairie voles, are active only from spring through early autumn.
为什么感觉E是弱化题干啊。。。。题干说group size 季节性变化是由于幼崽死亡率的季节性变化。。。然后E说其实是由于蛇的捕食造成的，这不就变成第三方因素导致group size和幼崽死亡率的季节性变化吗。。
鄙视题目是我的不对，求赐教
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