Dr. Myers and Dr. worm argue that their work gives a correct baseline, which future management efforts must take into account. They believe the date support an idea current among marine biologists, that of the “shifting baseline”. The notion is that people have failed to detect the massive changes which have happened in the ocean because they have been looking back only a relatively short time into the past. That matters because theory suggests that the maximum sustainable yield that can be cropped form a fishery comes when the biomass of a target species is about 50% of its original levels. Most fisheries are well below that, which is a bad way to de business.

　　31.The extinction of large prehistoric animals is noted to suggest that

　　[A] large animal were vulnerable to the changing environment

　　[B] small species survived as large animals disappeared

　　[C] large sea animals may face the same threat today.

　　[D] Slow-growing fish outlive fast-growing ones

　　[答案] C

　　[解题思路]

　　本题要求判断史前大型动物的灭绝这个例子所暗示的内容。乍一看似乎四个选项都各有道理，因此我们要定位原文信息。文章第一段主要介绍了这些大型动物灭绝的原因，同时该段最后一句话指出“Now something similar could be happening in the oceans”(现在同样的事情可能正在海洋中发生)，也就是说，现在海洋中的大型动物也正面临着史前大型动物曾经面临的威胁。因此文章开篇是通过类比手法来引出主题，C选项符合题意。A、B、D都不符合第一段中提供的信息。

　　[题目译文]