What at that time ?-Playing football.A. did you doB. do you doC. were you doingD. are y

问题补充：

What at that time ? ---Playing football.

A. did you do

B. do you do

C. were you doing

D. are you doing

答案：

A. did you do

B. do you do

(答案→)C. were you doing

D. are you doing

解析：句意：那时你正在做什么？——踢足球。根据答语及上文时间状语，可知本句描述的是过去某时正在进行的动作，故用过去进行时态，选C。