In fact he had done ______ he could do to help the poor.
A、what
B、which
C、as
D、all which
【正确答案】：A
【题目解析】：本句缺的是宾语，选A组成一个what引导的名词从句充当宾语。 what he could to help the poor＝the things that/which he could do to help the poor，即 the things作前面done的宾语，而that或which代替the things作后面could (do)的宾语，do被省略了。D项all后面的定语从句的引导词只能是that。
