时间状语从句
时间状语从句常由以下连接词引导：when（当……时），as（一边……一边；当…时），while（在……期间），after（在……之后），before（在……之前），as soon as（一……就），since（自从），till(until)（直到……，直到……才），whenever（任何时候），the moment（一……就），no sooner than（一……就），hardly…when…（一……就）等。由以上连接词（或词组）连接的主从复合句中，主句和从句的动作，有的是同时发生，有的是先后发生。因此，要特别注意根据连接词所代表的时间不同，主句和从句的谓语要使用相应的时态。这是掌握时间状语从句的关键。
1. when 和 whenever 引导的从句：从句的动作和主句的动作可以同时发生，也可以先于主句的动作发生。例如：When we reached home, it was already dark.我们到家的时候天已经黑了。
When my cousin came yesterday, I was playing volleyball.昨天我表哥来时，我正在打排球。
When it rains, I go to school by bus.下雨的时候，我坐车去学校。
I shall tell her the good news when she comes.
她来时，我将告诉她这个好消息。（主从句都表示将来发生的动作，但要注意从句中要用一般现在时，表示将来。）
Come to e us whenever you can.你什么时候有空，就过来看看我们。
2. while 和 as 引导的从句：while表示“当…过程中”，强调某一段时间主句和从句的动作在同时发生。as表示“当…时”或“一边…一边”，主句和从句的动作同时发生。例如：
Work while you work; play while you play.该工作的时候就工作，该玩的时候就玩。
While he is reading, he always makes notes.他经常一面看书，一面做笔记。
She sings as she goes along.她边走边唱。
You will grow wir as you grow older.随着年龄的增长，你会更加聪明起来。
3. before 和 after 引导的从句：前者一般表示主句的动作发生在从句动作之前。后者表示
主句的动作发生在从句动作之后。例如：I didn’t know any English before I came here.我来这儿之前，一点英语都不懂。
I had written my report before my mother came back.我母亲回来之前，我已写完我的报告。
It will be long before we meet again.我们要过很久才能见面。
After he locked the door, he left.他锁上门，就走了。
After he had finished his work, he played a game of chess with his friend.
他工作完成以后，与朋友下了一会儿棋。
After you think it over, plea let me know your decision.你想好以后，请告诉我你的决定。
4. till和 until 引导的从句：表示“直到…”，主句和从句都为肯定式时，till和untill都可用；表示“直到…才”，主句用否定式，从句用肯定式,一般用untill。例如：
They worked till(until) it was dark. 他们一直工作到天黑。
She didn’t go to bed until she had reviewed her lessons.她直到复习完功课才睡觉。
Not until I shouted at the top of my voice did he turn his head.
直到我高声喊叫，他才转过头来。(Not until放在句首时,主句的谓语动词要倒装.) (参见第十四课)
5. since和 ever since 引导的从句：表示“自从以来”，从句一般表示动作的起点，用过去时。主句表示动作延续的情况，一般用现在完成时或现在完成进行时。如果主句表示的是时间时,主句可用一般现在时，也可用现在完成时。例如：
Since he entered the university, he has made great progress in his studies.
自从他上大学以来，他在学习上取得了巨大的进步。
He has been working here ever since he left university.自从大学毕业以后，他就一直在这里工作。
It is/has been twenty years since she joined the Party.她入党二十年了。
It is/has been more than four weeks since school began.开学已经四个多星期了。
6. 短语连词 as soon as, , han, hardly(scarcely)...when引导的从句： 这些短语连词表示“一…就”或“刚一…就”。由han 和hardly(scarcely)...when引导的从句一般用过去完成时，主句一般用一般过去时。han 或hardly(scarcely)...when位于句首时，句子需部分倒装(参见第十四课)。 例如：
I’ll tell him the news as soon as I e him.我一看见他就告诉他这个消息。
As soon as she came to the classroom, she began to read English.她一来到教室，就开始读英语。
The bell had no sooner rung than the students quieted down.铃声一响，学生们就安静下来了。
The examinee had scarcely finished the test when the bell rang.
这位考生刚做完考卷,铃声就响了.
Hardly(Scarcely) had he entered the classroom when the teacher began his lecture.
他刚走进教室，老师就开始讲课了。
No sooner had they got to the plant than they started to work.他们一到工厂就开始工作.
7. 副词once, now (that), immediately, instantly, directly 引导的从句： 这些副词表示“一…就”，其含义相当于as soon as。 例如：Once you understand this rule, you will have no further difficulty.
你一旦了解这个规则，就不会再有困难。
Now (that) you mention it, I do remember.你一提，我就记起来了。
I told him immediately he came.他一来我就告诉他了。
Instantly I arrived there I telegraphed him.我一到那里就给他发了电报。
Directly I heard the news, I hastened to the spot.我一听到消息就赶到了现场。
8. 名词短语every time, each time, the (very) moment, the instant, the minute (that)和介词短语 by the time (that) 引导的从句。例如：Every time I went there, he was there.我每次到那里，他都在那里。
Each time I called on him, he was busy with his work.我每次去看他，他都在忙于工作。
I recognized you the moment I saw you.我一见到你，就认出你来了。
I’ll tell him the minute he comes.他一来我就告诉他。
The instant the soldiers heard the alarm, they fell in for action.战士们一听到是警报，就立即行动准备战斗。
Anything written about electronics will probably be at least partially out of date by the time it appears in print. 任何有关电子学的东西等到印成书出版时,很可能至少部分东西已过时了.
( ) 1. While she ____ TV in the sitting room, the bell _____.
A. watches, rings B. is watching, rang C. was watching, rang
2. I ____ you the news as soon as you ____ Xi’an. A. will tell, reach B. tell, will arrive in C. will tell, will get to
