I was about to leave my housethe phone rang. A. whileB. whenC. asD. after

问题补充：

I was about to leave my housethe phone rang.

A. while

B. when

C. as

D. after

答案：

A. while

(答案→)B. when

C. as

D. after

解析：be about to do与when连用。该题里面没有状语从句, when是一个并列连词，提供额外信息，常容易和时间状语从句混淆。