问题补充：
I my homework while my parents TV last night.
A. did; have watched
B. was doing; were watching
C. had done; were watching
D. would do ;were watching
答案：
A. did; have watched
(答案→)B. was doing; were watching
C. had done; were watching
D. would do ;were watching
解析：while 连接前后的动作为同时发生的动作，故选B
