when表突然意思时候的几个固定用法

问题描述:

when表突然意思时候的几个固定用法
好像有be about to do.when 还有我就想不起来啦 多谢大家帮帮忙

通常主句为过去进行时,从句为一般过去时

i was having my dinner when there was a sudden
knock at the dorr