I my homework while my mother was reading a book last night.A. didB. doC. was doingD. were

问题补充：

I my homework while my mother was reading a book last night.

A. did

B. do

C. was doing

D. were doing

答案：

A. did

B. do

(答案→)C. was doing

D. were doing

解析：句意：昨晚当我的母亲正在读书时，我正在做作业。While引导时间状语从句时，强调动作的同时发生，结合语境可知主句描述的是过去正在进行的动作，句子主语是I，故助动词用am的过去时态was，选C。