新prep2-69

liuqiangde

69.   (25194-!-item-!-188;#058&001228)

 

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

答案是B，请帮忙看一下为什么，多谢了。

pdsb

可能是这样吧

上面说：1.如果动物被大规模捕猎，则这个动物种群里性早熟的家伙会变多。
        2.如果动物缺食物，则性晚熟的家伙会变多。
        3.人们用这个原理可以知道远古的这种象的消失到底是因为捕猎呢，还是因为没吃的？

紧接着B项说：象性成熟的平均年龄可以从象牙推测出来，而且象牙化石很多，分布的年代又广泛。

这样人就可以从不同年代的象牙化石中推测出那时象性成熟的年龄，知道它们到底是性成熟的早还是晚，进而推测出是被捕杀的还是饿死的
       

liuqiangde

明白了，谢谢。

大帅Nick

wo ye xiang wen zhei ge