— What were you and your sister doing when the telephone rang?— I while my sister was eati

问题补充：

— What were you and your sister doing when the telephone rang?

— I while my sister was eating.

A. sleep

B. am sleeping

C. slept

D. was sleeping

答案：

A. sleep

B. am sleeping

C. slept

(答案→)D. was sleeping

解析：句意：当电话响时，你和你的妹妹正在做什么?结合语境可知下文描述的是过去某时正在进行的动作，故用过去进行时态，选D。