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题库 / Prep2007E1-SC-136
It seems likely that a number of astronomical phenomena, such as the formation of planetary nebulas, may be caused by the interaction where two stars orbit each other at close range.
may be caused by the interaction where two stars orbit each other
may be caused by the interaction between two stars that each orbit the other
are because of the interaction between two stars that orbit each other
are caused by the interaction of two stars where each is orbiting the other
are caused by the interaction of two stars orbiting each other
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a number of这种表示数量的词（ hundreds of/）的核心词是后面的名词，但是“the number of ” “the proportion of”为xx数量，所以以number和数量为主
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