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  3. Certainly no creature in the sea is odder than the common sea cucumber. All living creatures, especially human beings, have thei

Certainly no creature in the sea is odder than the common sea cucumber. All living creatures, especially human beings, have thei

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问题      Certainly no creature in the sea is odder than the common sea cucumber. All living creatures, especially human beings, have their peculiarities, but everything about the little sea cucumber seems unusual. What else can be said about a bizarre animal that, among other eccentricities, eats mud, feeds almost continuously day and night but can live without eating for long periods, and can be poisonous but is considered supremely edible by gourmets?
     For some fifty million years, despite all its eccentricities, the sea cucumber has subsisted on its diet of mud. It is adaptable enough to live attached to rocks by its tube feet, under rocks in shallow water, or on the surface of mud flats. Common in cool water on both Atlantic and Pacific shores, it has the ability to suck up mud or sand and digest whatever nutrients are present.
     Sea cucumbers come in a variety of colors, ranging from black to reddish brown to sand color and nearly white. One form eyen has vivid purple tentacles. Usually the creatures are cucumber shaped -- hence their name — and because they are typically rock inhabitants, this shape, combined with flexibility, enables them to squeeze into crevices where they are safe from predators and ocean currents.
     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. If it were not for this faculty, they would devour all the food available in a short time and would probably starve themselves out of existence.
     But the most spectacular thing about the sea cucumber is the way it defends itself. Its major enemies are fish and crabs. When attacked, it squirts all its internal organs into water. It also casts off attached structures such as tentacles. The sea cucumber will eviscerate and regenerate itself if it is attacked or even touched; it will do the same if the surrounding water temperature is too high or if the water becomes too polluted.  
The fourth paragraph of the passage primarily discusses ______.
选项 A、the reproduction of sea cucumbers
B、the food sources of sea cucumbers
C、the eating habits of sea cucumbers
D、threats to sea cucumbers’ existence
答案C
解析 主旨大意题。参考译文的第四段可以得知，本段的主要内容可以归结为海参的进食习惯。选项A和D 的内容是第五段讲的，而选项B在第二段已经提到。
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