问题补充：
when the light went on last night?
A. What were you doing
B. What have you done
C. What did you do
D. How were you doing
答案：
(答案→)A. What were you doing
B. What have you done
C. What did you do
D. How were you doing
解析：句意：昨天夜晚，当灯亮的时候你正在做什么？时间限定在一段时间之间，应用进行时，由于是过去的动作，固用过去进行时，故选A.
