Question

Is that old man _ you often help with his housework. 选哪一个

A. / B. as C. why D. the one

Answer 1

D，这是定语从句的只是，先把句子变为肯定句，只能是That old man is ______ you often ....
这个句子中is缺表语（同时又是后面定语从句的先行词），后面的help缺少宾语，所以应该用the one who/that, 做宾语时that'或who省略了
那个老人是不是你经常帮他做家务的？
如果句子是Is that the old man....，这样就选A(因为改为肯定就是That is the old man ...,只缺一个引导词who或that，省略