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2024年12月英语四级语法常识：过去完成时
1) 定义：表示过去的过去
----|-------|-----|---->其构成是had +过去分词构成。
那时以前 那时目前
2) 使用方法
a.在told, said, knew, heard, thought等动词后的宾语从句。
She said she had never been to Paris.
b. 状语从句
在过去不同时间发生的两个动作中，发生在先，用过去完成时;发生在后，用一般过去时。
When the police arrived, the thieves had run away.
c. 表示意向的动词，如hope, wish, expect, think, intend, mean, suppose等，用过去完成时表示"原本…，未能…"
We had hoped that you would come, but you didnt.
3)过去完成时的时间状语before, by, until , when, after, once, as soon as。
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.
典型例题
The students ___ busily when Miss Brown went to get a book she ___ in the office.
A. had written, leftB，were writing, has left C. had written, had leftD. were writing, had left
答案D. "把书忘在办公室"发生在"去取书"这一过去的动作之前，因此"忘了书"这一动作发生在过去的过去，用过去完成时。句中when表示的是时间的一点，表示在"同学们正忙于……"这一背景下，when所引导的动作发生。因此
前一句应用过去进行时。
注意：had no … when还没有等…… 就……
had no sooner… than刚…… 就……
He had no sooner bought the car than he sold it.
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