If half of the water were to be drained from the Pacific Ocean, a curious kind of submarine mountain called a guyot(海底平顶山)would

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问题     If half of the water were to be drained from the Pacific Ocean, a curious kind of submarine mountain called a guyot(海底平顶山)would be exposed. Guyots are strange formations that resemble mushroom stalks with flat tops. More than six hundred and fifty of these volcanic stalks have been discovered in the Pacific Ocean, and a few others have been discovered in the Atlantic sea plains .
    It is easy to suppose that the guyots were formed by underwater lava spouts that piled up volcanic debris(残骸)over the years, but just how they acquired their curiously flat tops remains a mystery. Shallow-water fossils found embedded(植入)in the tops of some guyots suggest that at one time the flat tops were much nearer the ocean’ s surface, but beyond this there is little that scientists can say.
    One attempt to account for the flat tops suggests that the ocean levels were once much lower than they are today; thus wave action might have smoothed away the original peaks. Another theory holds that the guyots have probably always flat tops and that their weight has pushed them slightly toward the ocean floor, causing them to slowly submerge . But these are only theories—the guyots are still a geophysical puzzle.
We can conclude from this passage that______.

选项 A、there are guyots in every ocean of the world
B、guyots are produced by violent volcanic action
C、the mystery of the guyots will soon be solved
D、the guyots’ flat tops will remain a mystery for some time

答案D

解析 文章中反复出现but just how theyacquired their curiously flat tops remains amystery,but beyond this there is little that scientistscan say.But these are only theories--the guyotsare still a geophysical puzzle.故选D。
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