2017全国英语等级考试二级语法知识
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用一般过去时代替完成时
1) 两个动作如按顺序发生，又不强调先后，或用then，and，but 等连词时，多用一般过去时。
When she saw the mouse，she screamed.
My aunt gave me a hat and I lost it.
2 ) 两个动作相继发生，可用一般过去时;如第一个动作需要若干时间完成，用过去完成时。
When I heard the news, I was very excited.
3) 叙述历史事实，可不用过去完成时，而只用一般过去时。
Our teacher told us that Columbus discovered America in 1492.
过去完成时典型例题
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 还没等…… 就……
had no sooner… than 刚…… 就……
He had no sooner bought the car than he sold it.
过去完成时
1) 概念：
表示过去的.过去
其构成是had +过去分词构成。
那时以前 那时 现在
2) 用法
a.在told, said, knew, heard, thought等动词后的宾语从句。
She said (that) 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 didn't.
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.
现在进行时
现在进行时的基本用法：
a. 表示现在( 指说话人说话时) 正在发生的事情。
We are waiting for you.
b. 习惯进行：表示长期的或重复性的动作，说话时动作未必正在进行。
Mr. Green is writing another novel.
(说话时并未在写，只处于写作的状态。)
She is learning piano under Mr. Smith.
c. 表示渐变的动词有：get, grow, become, turn, run, go, begin等。
The leaves are turning red.
It's getting warmer and warmer.
d. 与always, constantly, forever 等词连用，表示反复发生的动作或持续存在的状态，往往带有说话人的主观色彩。
You are always changing your mind.
典型例题
My dictionary ___, I have looked for it everywhere but still___ it.
A. has lost, don't findB. is missing, don't find C. has lost, haven't found D. is missing, haven't found.
答案D. 前句是一个仍在持续的状态，应用进行时，由于没有找到，其影响仍然存在，应用完成时，瞬间动词用于否定式时可用于完成时。
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