过去完成时:
1.概念:以过去某个时间为标准,在此以前发生的动作或行为,或在过去某动作之前完成的行为,即“过去的过去”。
2.时间状语:before, by the end of last year(term, month…),etc.
3.基本结构:had + done.
4.否定形式:had + not + done.
5.一般疑问句:had放于句首。
6.例句:As soon as we got to the station, the train had left.
By the end of last month. We had reviewed four books
【数学之美】很高兴为你解答,不懂请追问!满意请采纳,谢谢!O(∩_∩)O~
追问也就是说只要出现before就是过完?
追答是的