第22题: [单项选择]I am sure Tom has been here and has done ______. A. that required him B. which was required of him C. what was required of him D. what has been required him 参考答案:C 答案解析:分析句子可以看出空格处为动词done的宾语部分。what可引导宾语从句,相当于the thing which。其中the thing为has done的宾语,which引导后面的内容作定语。而sth.