I was about to leave the telephone rang.A. afterB. whileC. whenD. before

问题补充：

I was about to leave the telephone rang.

A. after

B. while

C. when

D. before

答案：

A. after

B. while

(答案→)C. when

D. before

解析：考查固定句式。固定句式;be about to do sth when…正要做某事在这时…；when指在这时…；是一个并列连词。后面的句子表示意料之外的事情。句意：我正要离开，在这时电话响了。故C正确。