过去完成时的用法
一）经常使用过去完成时的情形：
1. 过去完成时表示在过去某一时间或动作以前已经完成了的动作。这个过去的时间常用by，before等介词短语或一个时间状语从句表示，也可以暗含在上下文中。
I had finished my homework before supper.
我在晚饭前就把作业做完了。
The play had already started when we got to the theatre.
我们到剧场时戏已经开始了。
By the end of June they had treated over 10,000 patients.
到六月底他们已经治疗了一万多病人。
By nine o’clock last night, we had got 200 pictures from the spaceship.
到昨晚9点钟，我们已经收到200 张飞船发来的图片。
2. 过去完成时还可表示过去某一时刻之前发生的动作或状态持续到过去某个时间或还要持续下去，常与for，since等词连用。如：
He had served in the army for ten years before he retired last year.
他在部队干了十年，去年退役了。
He told me that he had known her since he was a child.
他告诉我他从小就认识她。
He had learned English for eight years before he went to England for further study.
他在去英国深造前，已学了八年英语。
I had been at the bus stop for 20 minutes when a bus finally came.
当车来的时候，我在车站已等了20分钟。
He said he had worked in that factory since 1949.
他说自从1949年以来他就在那家工厂工作。
3. 叙述过去发生的事情，在已叙述了过去发生的事情后，反过来追述或补述以前发生的动作时，常使用过去完成时。如：
Tom flew home, but his father had already died.
汤姆乘飞机回家，他的父亲却已经去世了。
Mr. Smith died yesterday. He had been a good friend of mine.
史密斯先生昨天去世了。他以前是我的好友。
I didn’t know a thing about the verbs, for I had not studied my lesson.
我对动词一无所知，因为我没有好好学习功课。
4. 在含有定语从句的主从复合句中，如果叙述的是过去的事，先发生的动作常用过去完成时。例如：
I returned the book that I had borrowed.
我已归还了我借的书。
She found the key that she had lost.
她丢失的钥匙找到了。
5. 过去完成时常常用在told, said, knew, heard, thought等动词后的宾语从句（或间接引语）
中，这时从句中的动作发生在主句表示的过去的动作之前。例如：
He said that he had known her well.
他说他很熟悉她。
I thought I had sent the letter a week before.
我认为我一星期前就把信寄出去了。
6. 过去完成时也用于hardly...when..., no sooner...than..., It was the first time + that分句等一些固定句型中。
He had no sooner left the room than they began to talk about him.
他刚离开房间，他们就议论起他来。
We had hardly begun when we were told to stop.
我们刚开始就被叫停。
It was the first time that he had ever spoken to me in such a tune.
他用这样的语调跟我讲话，这是第一次。
二）不使用过去完成时的情形：
1、句中如yesterday , last year , in 1986 , three days ago等明确地表示过去时间的状语，谓语动词必须用一般过去时。例如：
Peter didn`t play football yesterday .
彼得昨天没有踢足球。
2、在叙述两件以上的事件时，如果事件之间连接地很紧凑的一系列的动作，一般仍用一般过去时而不用过去完成时。例如：
They decided to stay here , and so they built their houses and made their farms .
他们决定呆在这儿，所以他们建了房子，开垦了农场。
