过去完成时
The Past Perfect Tense
过去完成时的构成
过去完成时由"助动词had (通用于各种人称和数)＋过去分词"构成。主要表示过去某时前已发生的动作或情况（也可说是"过去的过去"）：
By the time I got there, it had already finished.
When I got to the check-out, I realized I had left my purse at home.
He said he had never seen such an exciting match before.
注：如果时间状语从句的动作发生在前，则从句用过去完成时，主句用一般过去时。
When he had finished his work , he left his office .
After I had done my homework , I went to bed.
陈述句
They had already had breakfast before they arrived at the hotel.
在他们到达旅馆之前，他们已经吃早饭了。
从句中"arrived at"到达在"过去"的时间，而"had already had"吃早饭的动作发生在到达之前，因此主句的时态为"过去的过去"。
I had finished writing my composition by 10:00 this morning. 今天上午10：00点以前，我已经写完了我的作文。
She had searched the internet for two hours when she found an ad for the Canon digital camera. 当她找到了佳能数码照相机的广告时，她已经在因特网上查询了两个小时。
I went over what I had written again and again so that I wouldn't make any mistakes. 我一遍又一遍地检查了我所写的内容，以至我没有出现任何错误。
否定句
He remembered he hadn't paid for it yet. 他记得他还没有付账。
He said that he had never seen such a beautiful bird before.
他说他以前从来没有看过这样美丽的鸟。
疑问句
How many English films had you seen by the end of last term?
到上学期期末为止，你们看了多少部英文片？
Had you reached the station before ten o'clock?
十点以前，你们已经到达火车站了吗？