— I don’t understand why you didn’t go to the lecture yesterday afternoon.
A. had done
B. was doing
C. would do
D. am doing
网友回答
A. had done
(答案→)B. was doing
C. would do
D. am doing
解析：句意：－我不懂你为什么没参加昨天下午的讲座。－真抱歉，那时我正在做作业。指昨天下午“那时”发生的事，故用过去进行时态。
【考点定位】考查动词的过去进行时态。