过去完成式 (had + p.p.)

在过去某个时间或某个动作发生之前的动作

Tina had already left when I got there.

当我到的时候Tina已经离开了。

Tina had gone home before I arrived there.

Tina在我到达之前就已经回家了。

The train had left before I got to the station.

我到火车站时那班火车已经离站了。

He had studied French for two years before he went to France.

他去法国前已学了两年的法文了。

I didn't go to see the movie "The Sound of Music" with my daughter yesterday because I had already seen the film twice.

昨天我没跟女儿去看电影《真善美》，因为我已经看过两遍了。