过去完成进行时是什么?用法呢?
问题描述：
过去完成进行时是什么?用法呢?
答
形式：had been doing
答
过去完成进行时表示过去某一时刻之前开始的动作或状态一直延续到过去某一时刻.例如：
It had been raining cats and dogs for over a week and the downpour had caused landslides in many places.