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.

(A) may be caused by the interaction where two stars orbit each other

(B) may be caused by the interaction between two stars that each orbit the other

(C) are because of the interaction between two stars that orbit each other

(D) are caused by the interaction of two stars where each is orbiting the other

(E) are caused by the interaction of two stars orbiting each other

And here is the explaination on OG regarding choice C : Also, the phrase two stars that orbit each other illogically suggests that there are two particular stars causing all the phenomena in question, rather than various sets of stars in various locations.

Just don't understand what's the difference between stars that orbit.... and stars orbiting..... Shouldn't they be the same?

Thank you so much in advance........

我记得这道题的关键不在你问的这个问题，是interaction 的用法

interaction后面不能跟between的，查字典就知道了

关于你问的问题，我觉得它们在意思上表达是一样的

不是牛人，一点意见仅供参考

除固定搭配外，一般来讲，动名词修饰名词表达属性，或是一个持续的动作状态，that修饰名词表达一次性的动作含义。而orbit显然不是一个一次性的动作，所以排除以that修饰的选项。

另外我觉得这题的考点在orbit和between的语义重复上，因为orbit就一定是两个球体之间的运动，加了between就违犯了ETS的 不简洁 原则。

完全是我个人的意见，不一定正确喔。