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 becaust of mutual gravitational attraction. A. repeated impacts broke the surface apart, and after which the fragments were subsequently rejoined becaust 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. A. and作連詞已經可以連接句子，and連接的兩個句子屬於同一層次；又出現after
which再次扮演連 詞的成分，連接的句子屬於子句，與主句構成主從關係。因此，該選項句子結構混亂；
prep解释里是这样说的
有两个问题
(1) after不也可以当介词吗?
(2) 这里的which是指代什么?
看句义感觉是前面句子the surface broke apart
虽然每个选项都有which
可是which不能指代句子不是GMAT的天理吗?
还是另外有所指呢? | 
