GMAT逻辑题

Theprairievole,asmallNorthAmericangrasslandrodent,breedsyear-round,andagroupofvoleslivingtogetherconsistsprimarilyofanextendedfamily,oftenincludingtwoormorelitters.Volescommonlyliveinlargegroupsfromlateautumnthroughwinter;fromspringthroughearlyautumn,however,mostvolesliveinfarsmallergroups.Theseasonalvariationingroupsizecanprobablybeexplainedbyaseasonalvariationinmortalityamongyoungvoles.

Whichofthefollowing,iftrue,providesthestrongestsupportfortheexplanationoffered?

(A)Itisinthespringandearlysummerthatprairievolecommunitiesgenerallycontainthehighestproportionofyoungvoles.

(B)Prairievolepopulationsvarydramaticallyinsizefromyeartoyear.

(C)Theprairievolesubsistsprimarilyonbroad-leavedplantsthatareabundantonlyinspring.

(D)Wintersintheprairievoles'habitatareoftenharsh,withtemperaturesthatdropwellbelowfreezing.

(E)Snakes,amajorpredatorofyoungprairievoles,areactiveonlyfromspringthroughearlyautumn.

正确答案是E,我错选了D,看了一下晚上的解析,有些地方还是有点不明白,能不能帮忙解答一下,

CD论坛上说根据文章所给的信息可得从晚秋到冬天vole的总数量比从春天到早秋的总数量要多,是不是根据“olescommonlyliveinlargegroupsfromlateautumnthroughwinter;fromspringthroughearlyautumn,however,mostvolesliveinfarsmallergroups.”这句话得到这个结论的（因为我一开始看到这句话的时候不小心又加了自己的想法以及自己的背景知识,所以貌似又想歪掉了.然后再根据文章最后一句话是不是可以得出youngvole死亡率高的时候,数量少,死亡率低的时候数量多,那么也就是说是冬天死亡率低,夏天死亡率高.然后E的选项正好能解释为什么春天到早秋死亡率高的原因,也就是捕食youngvole造成其死亡率上升,对结论做出了加强,所以E是正确选项,而D的话只说了冬天环境变差,并没有说环境变差与死亡率之间的的关系（在不用背景知识的情况下）,因此不能对结论做出支持,是无关选项,