Tom's mother kept telling him that he should work harder,but( )didn't help

问题描述:

Tom's mother kept telling him that he should work harder,but( )didn't help
A.it B.she C.which D.he
如果but去掉的话,是不是应该选C?

去掉后选C
原题选A
这是定语从句与并列句的转换啊.