由had 完成否定和疑问

1. 表示过去某动作或某个具体时间之前已经发生、完成的动作。“过去的过去”。

 ●They had got everything ready before I came. (因为before引导的时间状语动作先后很明确，也可只用一般过去时：They got everything ready before I came.)

 ●The play had begun before I got to the theater. (也可以The play began before I arrived.)

2. 过去完成时常用于hardly/scarcely... when, no sooner… than 等固定句型结构中。（VERY IMPORTANT，意为：“一…… 就”）

 ●She had hardly/scarcely gone to bed when the bell rang.

 ●No sooner had he arrived at the railway station than he met her parents.（注意no sooner在句首时句型倒装。）

3. intend（打算），mean（意味）， hope（希望）， want（想要）， plan（计划）等动词的过去完成时用来表示本打算做而没有做的事。

 ●I had intended to call on you yesterday, but someone came to see me just when I was about to leave.（……原想昨天去看你……）

 ●They had planned to hold a football match last week, but they had to cancel it because of bad weather.（……原计划上周举行一场足球赛……）

比较：过去完成一般时与进行时

Ø. The girl had cleaned up the room, so it was tidy.

Ø. The girl had been clearing up the room, so we had to wait outside.