he did all __he can ___the old man A what to save B \ to help C \ save D what help

问题描述:

he did all __he can ___the old man A what to save B \ to help C \ save D what help
第一个空为什么不填 what

选B 这是定语从句,定语从句这里先行词做宾语省略了
如果没有all 才可以用what ,那样的话是一个宾语从句 he diid what he can