prep 2#88 which的指代不明吧

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88.   Because Miranda, the smallest moon of Uranus, has a large number of different surface features, including craters, mountains, valleys, and fractures, some astronomers suggest that at one time repeated impacts broke the surface apart, and after which the fragments were subsequently rejoined because of mutual gravitational attraction.

(A) repeated impacts broke the surface apart, and after which the fragments were subsequently rejoined because of

(B) repeated impacts on the surface broke it apart, after which the fragments having rejoined with

(C) through repeated impacts that the surface broke apart, after which the fragments subsequently rejoined by

(D) the surface broke apart with repeated impacts, after which the fragments having rejoined through

(E) the surface broke apart as a result of repeated impacts, after which the fragments rejoined through

E Which 指代不明吧

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难道是指代前句么？which不能指代前句吧。所以我觉得应该指代的是surface broke apart这件事情，而在E里面是不是就指代了repeated impacts了呀？

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定～