题目选项分析

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 the surface broke apart as a result of repeated impacts, after which the fragments rejoined through mutual gravitational attraction.

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 on the surface broke it apart, after which the fragments having rejoined with mutual gravitational attraction.