2. The fourth paragraph of the passage primarily discusses ______.
C
[解析] 题目问:文章第四段主要讨论什么内容?第四段Although they have voracious appetites, eating day and night, sea cucumbers have the capacity to become quiescent and live at a low metabolic rate—feeding sparingly or not at all for long periods, so that the marine organisms that provide their food have a chance to multiply.通过这句话可知,虽然海参有一个贪婪的胃,它们能整日地进食,但是由于它们能够以很低的新陈代谢水平生存,所以又能很长时间不进食。据此判断,应选择C。