——Why is the classroom so dirty?
——Sorry, Sir. It yesterday. We forgot to do it.
A. doesn’t clean
B. didn’t clean
C. isn’t cleaned
D. wasn’t cleaned
网友回答
A. doesn’t clean
B. didn’t clean
C. isn’t cleaned
(答案→)D. wasn’t cleaned
解析：根据句意，本题应用被动语态，即“教室被打扫”，而时间是yesterday，故用一般过去时的被动语态，选D。