问题补充:
It was very kind of you to do the washing up, but you it.
A. mustn have done
B. wouldn have done
C. mightn have done
D. didn have to do
答案:
A. mustn have done
B. wouldn have done
C. mightn have done
(答案→)D. didn have to do
解析:考查情态动词和虚拟语气的用法。don have to do sth.“不必做某事”。也可以说needn have done it。