GMAT Thepopulation of elephant seals,reduced by hunting to p

GMAT
Thepopulation of elephant seals,reduced by hunting to perhaps a few dozen animalsearly in this century,has soared under federal protection during the last fewdecades.However,because the species repopulated itself through extensiveinbreeding,it now exhibits a genetic uniformity that is almost unparalleled inother species of mammals,and thus it is in far greater danger of becomingextinct than are most other species.
Given theinformation in the passage above,which of the following is most likely thereason that other species of mammals are less likely than elephant seals tobecome extinct?
A.Otherspecies of mammals have large populations,so the loss of a few members of thespecies is not significant.
B.Otherspecies of mammals have increased their knowledge of dangers though theexperience of generation after generation of animals.
C.In otherspecies of mammals,hunters can readily distinguish between males and femalesor between young animals and adults.
D.In other species of mammals,some members of thespecies are genetically better equipped to withstand a disease or event thatdestroys other members of the species.
E.Otherspecies of mammals have retained habits of caution and alertness because theyhave not been protected as endangered species.
为什么答案选D 求详解.

文章翻译：海象的数量之前由于捕杀而大量下降,后.来由于联邦的保护而回升.然而这个种群通过近亲繁殖,有一种基因的一致性,而这种一致性在其他种类的动物身上是很少见的.所以这就是为什么海象比其他动物更容易灭绝的原因.
　　文章解析：
　　这是一道解释现象的题目,需要你解释的就是为什么其他种类的生物与海象比更不容易灭绝,在文中能找到对应的内容,即文章最后一句话：这就是海象比其他动物更容易灭绝的原因.那么解释的原因是一样的,就是海象基因的一致性导致他们更容易灭绝.
　　选项分析：
　　A.其他种群的动物数量比较多,少一两个并不重要.这个不是文章给出的解释.
　　B.其他种类的哺乳动物关于危险的知识随着世代相传增加.无关项.
　　C.其他种类的哺乳动物中,猎人很难分清公母以及长幼.无关项.
　　D.其他种类的哺乳动物,一些成员在基因上可以很好的抵御一次事件或者是疾病,而这次事件或者是疾病足以毁掉种族内的其他成员.也就是说,其他种族的哺乳动物由于基因的多样性而得以存活,正是文中所要表达的意思.正确答案.
　　E.其他哺乳动物不是濒危物种而没有受到联邦的保护,因此他们一直保持着警觉性.无关项.