.He was about to leave the telephone rang; was from his mother.
A. when; that
B. before; which
C. when; it
D. before; this
网友回答
A. when; that
B. before; which
(答案→)C. when; it
D. before; this
解析：句意：他即将离开这是电话响了，是母亲打来的。句型： be about to do …when，即将做某事，正在那时，第二空用it ，指代前面的电话，所以选C。