The old man has two sons,______ are lawyers.

问题描述:

The old man has two sons,______ are lawyers.
   A.both of them  
  B.both of who  
  C.both of whom
  D.both of they
这题不选AD是因为如果选了AD,没有连词,同时出现了主谓不可以.
为什么不选B?B不是既可以做主语又可以做宾语吗?who做of的宾语,同时也做了are的主语

详细讲下两个问题,

本句的主语为the old man,如果选AD是主谓不一致.
BC,who和whom同时在选项的时候,作宾语优先选whom
选c