概念： 表示過去的過去，其構成是had +過去分詞。　　

一、過去完成時常用的連詞有： before, by, until, when, after, once, as soon as等。例如：

He said that he had learned some English before.

By the time he was twelve, Edison had began to make a living by himself.

Tom was disappointed that most of the guests had left when he arrived at the party.

二、在什么情況下使用過去完成時？

1. 在told, said, knew, heard, thought等動詞引導的賓語從句中，一般用過去完成時。例如：

She said (that) she had never been to Paris.

2. 狀語從句

在過去不同時間發生的兩個動作中，發生在先，用過去完成時；發生在后，用一般過去時。例如：

When the police arrived, the thieves had run away.

3. 表示意向的動詞，如hope, wish, expect, think, intend, mean, suppose等，用過去完成時表示“原本……，未能……”。例如：

We had hoped that you would come, but you didn't.

典型例題：

The students ________ busily when Miss Brown went to get a book she ____ in the office.

A. had written, left

B. were writing, has left

C. had written, had left

D. were writing, had left

答案D。 “把書忘在辦公室”發生在“去取書”這一過去的動作之前，因此“忘了書”這一動作發生在過去的過去，用過去完成時。句中when代表時間的一點，表示在“同學們正忙于……”這一背景下， when所引導的動作正在發生。因此前一句應用過去進行時。