问题补充:
--- Why on earth didn’t you answer the door?
--- I’m terribly sorry, but the telephone , too.
A. is ringing
B. was ringing
C. rang
D. was about to ring
答案:
A. is ringing
(答案→)B. was ringing
C. rang
D. was about to ring
解析:表示过去某一时间正在进行的动作,用过去进行时,故选B。