定于从句练习

题目

定于从句练习
The doctor did all_to save de wounded boy.
A.what he could B.he could C.everything which he could D.for which he could
为啥选B?先行词all 在从句中做什么成分呢?为什么不是填he could do?

答案

先行词在从句中是不做成分的,完整的从句是：the doctor did all that he could did to save the wounded boy.但是主语 the doctor 后面已经有一个did了,所以从句中的did被省略了,所以此处 he could 和 he could do ...