While he his homework his mother came in.A. doesB. didC. was doingD. do

问题补充：

While he his homework , his mother came in.

A. does

B. did

C. was doing

D. do

答案：

A. does

B. did

(答案→)C. was doing

D. do

解析：while 引导的时间状语从句，从句往往用进行时态，故选C