I( )leave when the telephone rang.Awas going to Bwas to Cwas about to Dwill

应该是选C吧
首先排除D
A通常不这样用 而用I was leaving when the telephone rang.
B be to 表示计划、打算做某事或者是命中注定做某事.一般表示将来的某些计划,后面可以加上时间限制的状语,如next week,next Friday等
C was about to 多指马上要做某事,即将做某事,不能与表示明确时间的短语搭配
was about to……when……是个固定搭配,这里when是个并列连词,可以理解为at that time
关于这题我的理解为,就在我要出门的那个时间点上,电话响了.我觉得我马上要出门这里的语境最符合,C恰好表示即将,马上的意思.
I was about to leave and at that time the telephone rang.