I my homework when the lights in my room went out last night.A. didB. was doingC. will do

问题补充：

I my homework when the lights in my room went out last night.

A. did

B. was doing

C. will do

D. have done

答案：

A. did

(答案→)B. was doing

C. will do

D. have done

解析：句意：当灯光突然熄灭的时候，我正在做作业。when 引导的从句表示一个时间点，强调在这个时间点上另一个动作正在发生。灯光熄灭是在过去，故我写作业用过去进行时，故选B。