—What were you doing when I called you at 8 p.m. yesterday?—I the piano at that time.A. pl

问题补充：

—What were you doing when I called you at 8 p.m. yesterday?

—I the piano at that time.

A. play

B. is playing

C. played

D. was playing

答案：

A. play

B. is playing

C. played

(答案→)D. was playing

解析：句意：- 昨天我八点给你打电话是你在做什么？那时我正在弹钢琴。at that time在那时，过去进行时的时间标志，其结构是：were/was+doing,故选D。