527.I'm sorry,but I don't quite follow you.Did you say you wanted to return on September 20?
Sorry,I ______ myself clear.We want to return on October 20.
A.hadn't made
B.wouldn't make
C.don't make
D.haven't made
528.It took me a long time before I was able to fully appreciate what they _______ for me.
A.had done
B.did
C.would do
D.were doing
527.答案是D;根据句意，此处可用didn't make或者haven't made。
528.答案是A;整个句子时态是一般过去时，他们对我的帮助则是过去的过去，因此选A。
