While Helen the guitar her mother came in.A. was playingB. is playingC. playedD. plays

问题补充：

While Helen the guitar, her mother came in.

A. was playing

B. is playing

C. played

D. plays

答案：

(答案→)A. was playing

B. is playing

C. played

D. plays

解析：while引导时间状语从句，常用进行时态。