Yesterday evening I was about to go to bed you phoned me.A. whenB. whileC. asD. but

问题补充：

Yesterday evening, I was about to go to bed you phoned me.

A. when

B. while

C. as

D. but

答案：

(答案→)A. when

B. while

C. as

D. but

解析：be about to do / be doing … when … 表示一个动作将要发生或正在发生时突然一个新动作出现使原来进行的动作被打断，这种意义的句子只能用when来引导从句。[来源:]