[求助]885-11-14

14.   In the late seventh century, in a dispute over whether the Prophet Muhammad’s son-in-law, Ali, should carry on as the fourth caliph, Muhammad’s successor, Islam split into two branches, the Sunnis and the Shiites.

(A) over whether the Prophet Muhammad’s son-in-law, Ali, should carry on as the fourth caliph, Muhammad’s successor

(B) over if Ali, the Prophet Muhammad’s son-in-law, was going to carry on and be the fourth caliph, Muhammad’s successor

(C) over whether Ali, the Prophet Muhammad’s son-in-law, was going to carry on and be the fourth caliph, Muhammad’s successor

(D) as to whether the fourth caliph, Muhammad’s successor, is to be the Prophet Muhammad’s son-in-low, Ali（A）

(E) concerning if the fourth caliph, Muhammad’s successor, was to be the Prophet Muhammad’s son-in-law, Ali

请帮忙看一下为什么不选C呢？C与A有什么区别呢？

非常感谢！

carry on 和 be 重复意思了

carry on as the fourth caliph

be the fourth caliph