GWD 9-20
Which of the following most logically completes the reasoning?
Either food scarcity or excessive hunting can threaten a population of animals. If the
group faces food scarcity, individuals in the group will reach reproductive maturity later
than otherwise. If the group faces excessive hunting, individuals that reach reproductivematurity earlier will come to predominate. Therefore, it should be possible to determine
whether prehistoric mastodons became extinct because of food scarcity or human hunting,
since there are fossilized mastodon remains from both before and after mastodon
populations declined, and ______.
A. there are more fossilized mastodon remains from the period before mastodon
populations began to decline than from after that period
B. the average age at which mastodons from a given period reached reproductive
maturity can be established from their fossilized remains
C. it can be accurately estimated from fossilized remains when mastodons became
extinct
D. it is not known when humans first began hunting mastodons
E. climate changes may have gradually reduced the food available to mastodons
答案是E ，可是，我还是没有彻底搞懂，请大家再帮忙理理，为什么动物的遗迹都在数量下降的前后能说明是由于食物缺乏造成的呢？还有，如果是由于hunting造成的，那遗迹应该是怎么样的？ 谢谢先啦 | 
