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.
不明白，春天蛇多了，可以rodent的族群缺变小了，这不更容易让蛇吃了吗？
为什么选E啊 逻辑思路不理解 作者: sasha_wen 时间: 2009-12-21 21:17
我觉得题目与答案好奇怪，D加强E虚弱，等待解答，帮忙顶作者: girlwithwings 时间: 2009-12-22 08:25
这题是D削弱，E加强吧。 我的理解是 Group Size 大：late autumn through winter 小：from spring through early autumn 结论是季节的变化决定Group Size