问题补充：
-----The windows must have taken you quite a long time that day.
------Right. Theyfor weeks.
A. haven’t been cleaned
B. hadn’t been cleaned
C. didn’t clean
D. haven’t cleaned
答案：
A. haven’t been cleaned
(答案→)B. hadn’t been cleaned
C. didn’t clean
D. haven’t cleaned
解析：考察时态。根据must have taken you quite a long time可知，这是对过去的推测，所以没有打扫是发生在花很长时间打扫这个动作之前，即过去的过去。
