—Who telephoned you just now?— don’t know. I was about to answer the phone when it .A. ran

问题补充：

—Who telephoned you just now?

— don’t know. I was about to answer the phone when it .

A. rang up

B. rang off

C. hung on

D. rang back

答案：

A. rang up

(答案→)B. rang off

C. hung on

D. rang back

解析：考查短语辨析。rang up 打电话，rang off 挂断电话，hung on 稍等，别挂断，rang back 回电话，句意：刚才谁给你打电话了？不知道，我刚要接电话正在那时它挂断了。所以选B。