下面看这样一道题目：
Which of the following most logically completes the reasoning?
When species are extensively hunted, individuals that reach reproductive maturity early make up a larger proportion of the population, because they have a better chance of reproducing. When species face diminished food resources, on the other hand, individuals tend to take longer to reach reproductive maturity. These considerations may help settle whether the primary cause of the gradual disappearance of North America's mastodons, prehistoric animals related to elephants, was diminished food resources or human hunting, since __________.
(A). from the location of certain hunting weapons in juxtaposition with mastodon remains, it is possible to determine whether those weapons were used to hunt mastodons
(B). the average age at which mastodons reached reproductive maturity can be established from mastodon tusks, of which there are many fossils dating from different periods
(C). from the remains of mastodons already discovered, it can be accurately estimated when mastodons became extinct
(D). from tusks and other bones, it is possible to determine whether male and female mastodons reached reproductive maturity at about the same age
(E). it is possible to determine whether the earliest human dwellings constructed from mastodon tusks and bones come from an earlier period than the earliest hunting weapons unambiguously associated with mastodon remains
题干理解：
当物种面临被hunt时，繁殖成熟较早;当面临食物减少时，物种繁殖成熟较晚。这有助于解释美洲象消失的原因是hunting还是food减少。
题干逻辑关键：reproductive maturity 早、晚---mastodons消失原因(hunt、food)
题目要求：给出上述说法成立的原因。
选项分析：
A、从 hunt weapon 的位置可以确定这些weapons是否被用;与题干逻辑无关
B、mastodons 达到reproductive maturity 的average age 可以通过mastodons 不同时期的tusk化石得知;言外之意是“mastodons化石的reproductive maturity是早是晚是可以被判断出来，进而得知其消失属于何种原因 ”，有关。
C、从mastodons 的遗迹可以准确估计其是何时灭绝的;无关;
D、通过 tusks and other bones可以判断male and female mastodons 达到reproductive maturity 的年龄是否相同;仍旧不能判断是否繁殖早熟，无关。
E、用mastodon tusks and bones 建成的早期human dwellings早于与mastodon remains有关的早期hunting weapons ;与题干逻辑无关。
答案：选B。
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