I was listening to the music____there was a knock at the door.

题目

I was listening to the music____there was a knock at the door.
A.though B.when C.because D.until
为什么选B不选D,怎么可能一边敲门还比一边听歌啊.选D不是很符合情理麽?
尽量详细噢.

答案

选B when可以指“当”“这时”
我正在听音乐,这是有人在敲门
这是在考察过去进行时