3) since +从句　 Great changes have taken place here since you left.

4) It is +一段时间+ since从句

It is two years since I became a college student.

★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。

过去以前

过去

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.

When I arrived at the train station, the girl had already left.

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 begun to make a living by himself.

实战演练:

The students _________ their classroom when the visitors arrived.

A . have cleaned B. had cleaned C. was cleaned D. have been cleaned

★将来完成时

1) 构成will / be going to do sth.

2) 概念

a. 状态完成：表示某事继续到将来某一时为止一直有的状态。

b. 动作完成：表示将来某一时或另一个将来的动作之前，已经完成的动作或一获得的经验。

They will have been married for 20 years by then.

You will have reached Shanghai by this time tomorrow.

实战演练:

1. By the time you arrive in London, we _____in Europe for two weeks.

A shall stay

B have stayed

C will have stayed

Dhave been staying

2. By 2050 the level of industrial pollution_______dangerous levels in many cities.

A will have reached

B will has reached C will have reached

D will reach

★将来完成进行时

构成：主语+ shall/will have been doing

将来完成进行时表示动作从某一时间开始一直延续到将来某一时间。是否继续下去，要视上下文而定。这个时态常和表示将来某一时间的状语连用。如:

I shall have been working here in this city for six years by the end of this year. 到今年年底，我将在这个城市工作6年了

I will have been pursuing the girl for eight years by the end of this month. 到这个月月底,我追那个女孩将要满8年了.

★过去将来进行时

过去将来进行时表示就过去某一时间而言,将来某一时刻或某一段时间正在进行的动作,主要用于宾语从句中,尤其多用于间接引语中。

They said they would be coming.

他们说了他们要来的.

He asked me what I should be doing at six the next day.他问我次日六点将正在做什么.

09.23. It would be _C_ a risk to let the child go to school by himself.

A. following

B. passing

C. running

D. carrying

★过去完成进行时

过去完成进行时表示动作在过去某一时间之前开始，一直延续到这一过去时间。

和过去完成时一样，过去完成进行时也必须以一过去时间为前提。

I had been looking for it for days before I found it. 这东西我找了好多天才找着的。

★过去将来完成时

过去将来完成时表示在过去看来将来某时会已经完成的动作，它由“would+have+过去分词”构成。如：She said she’d have finished her exams by then. 她说到那时她会已经考完试了

I thought Sophia would have told you something. 我想索菲娅会已告诉你一地情况。