并列句+状语从句用法精讲

英语中并列句的四种类型
一、联合关系
常用的连词有and( 同，和), when(=and just at this time 就在这时，然后), not only…but (also)…( 不仅……而且…… ), neither…nor… （既不……也不……）等。

如：
He helps me and I help him. 他帮我，我帮他。

He not only gave us a lot of advice, but also helped us to study English. 他不仅给我们出很多建议并且还帮助我学英语。

I was just leaving when the telephone rang. 我正要离开，电话铃响了。

注：when 作这种用法时，主要用于was/were doing sth. when sth./sb. did; was/were about to do sth. when sth./sb. did; was/were on the point of doing sth. when sth./sb. did 等句型中，表示“当某人或某物正在或正要做某事，就在这时突然又发生了另一事”。

二、选择关系
常用的连词有or( 或者，否则), otherwise( 否则), or else( 否则), either...or( 不是……就是) 。

如：
Hurry up, or (else) you’ll be late. 快点，否则就会迟到了。

Will he still be there or will he have gone away? 你那时还在那里还是可能已经走了？
You must go early, otherwise you will miss the bus. 你好得早点走，否则就赶不上公共汽车了。

Either Tom is coming or his sisters are. 不是汤姆就是她的姐妹们要来。

三、转折关系
常用的连词有but( 但是，可是，只是因为), while( 而、却), yet( 可是) 等。

如：
It never rains but it pours. 祸不单行。

壹壹英语论坛
I like tea while she likes coffee. 我喜欢喝茶而她喜欢喝咖啡。

She said she would be late, yet she arrived on time. 她说她会迟到，但她却准时到达了。

She looks very young, but she is already in her 30’s. 她看上去很年轻, 可是她已三十多岁了。

此处，还有副词still( 仍然），however( 然而) 也表示转折关系。

He is good-natured; still I don''t like him. 他脾气很好, 可是我还是不喜欢他。

The book is expensive; however, it''s worth it. 这本书很贵；却很值。

注意：but, while 不与although 连用，但yet, still 可与although 连用。

Although she felt ill, she still went to work. 她虽然感觉不舒服，但她仍然去上班。

四、因果关系
常用的连词有for （因为）和so （所以，因此）等。

如：
I am thirsty, for it is hot. 我口渴，因为天气太热。

The manager was ill so I went in her place. 经理病了所以我代她去。

注意：so 不与because 连用
由从句担任的状语，在句子中可修饰谓语（或其它动词）、形容词、副词或是整个句子，它可以用来表示时间、地点、原因、目的、结果、条件、方式、比较、让步等。

状语从句是一较大的语法项目，也是近几年高考题中常见的一个重要试点。

高考中已考查了时间、让步、地点、条件、目的等状语从句，这些从句仍是今后高考热点，应作充分准备。

同时对方式状语从句也应引起重视。

（一）时间状语从句
表示时间的状语从句可由when, as, while, whenever, after, before, till (unti l), since, once, as soon as (或the moment ), by the time, no sooner … than, h ardly (scarcely) … when, every time等引导。

e.g. When I came into the office, the teachers were having a meeting.
He started as soon as he received the news.
Once you see him, you will never forget him.
No sooner had I gone to bed than I went to sleep.
（二）原因状语从句
原因状语从句是表示原因或理由的，引导这类从句的最常用的连词是because, since, as , now that（既然）等，for 表示因果关系时（它引导的不是从句）为并列连词，语气不如because强。

e.g. He is disappointed because he didn't get the position.
As it is raining, I will not go out.
Now that you mention it, I do remember.
（三）地点状语从句
引导地点状语从句的连词是where 和wherever等。

e.g. Sit wherever you like.
Make a mark where you have a question.
（四）目的状语从句
引导目的状语从句最常用的词（组）是so, so that（从句谓语常有情态动词）, in o rder that, in case（以防，以免）等。

e.g. Speak clearly, so that they may understand you.
She has bought the book in order that she could follow the TV lessons.
He left early in case he should miss the train.
（五）结果状语从句
结果状语从句是表示事态结果的从句，通常主句是原因，从句是结果。

由so that （从句谓语一般没有情态动词）, so … that, such … that等引导。

e.g. She was ill, so that she didn’t attend the meeting.
He was so excited that he could not say a word.
She is such a good teacher that everyone admires her.
（六）条件状语从句
条件状语从句分真实性（有可能实现的事情）与非真实性（条件与事实相反或者在说话者看来不大可能实现的事情）条件句。

引导条件状语从句的词（组）主要有if, unless, s o (as) long as, on condition that, so (as) far as, if only ( = if )。

注意：条件从句中的if 不能用whether替换。

e.g. If he is not in the office, he must be out for lunch.
You may borrow the book so long as you keep it clean.
So far as I know（据我所知）, he will be away for three months.
You can go swimming on condition that ( = if ) you don’t go too far away f rom the river bank.
If he had come a few minutes earlier, he could have seen her.
（七）让步状语从句
让步状语从句可由although, though, as, even if (though), however, whatever, whether … or, no matter who (when, what, …) 等引导。

注意：as引导的让步状语从句一般是倒装的。

e.g. Though he is a child, he knows a lot.
Child as he is, he knows a lot.
Whatever ( = No matter what ) you say, I’ll never change my mind.
（八）方式状语从句
方式状语从句常由as, as if (though), the way, rather than等引导。

e.g. You must do the exercise as I show you.
He acted as if nothing had happened.
（九）比较状语从句
比较状语从句常用than, so (as) … as, the more … the more等引导。

e.g. I have made a lot more mistakes than you have.
He smokes cigarettes as expensive as he can afford.
The busier he is, the happier he feels.
（十）使用状语从句时要注意的几个问题
1、在时间和条件（有时也在方式、让步等）从句中，主句是一般将来时，从句通常用一般现在时表示将来。

e.g. We’ll go outing if it doesn’t rain tomorrow.
I’ll write to you as soon as I get to Shanghai.
2、有些时间、地点、条件、方式或让步从句，如果从句的主语与主句主语一致（或虽不一致，是it），从句的谓语又包含动词be ，就可省略从句中的“主语 + be”部分。

e.g. When (he was) still a boy of ten, he had to work day and night.
If (you are) asked you may come in.
If (it is) necessary I’ll explain to you again.
3、注意区分不同从句：引导的是什么从句，不仅要根据连词，还要根据句子结构和句意来判别。

以where为例，能引导多种从句。

e.g. You are to find it where you left it.（地点状语从句）
Tell me the address where he lives.（定语从句，句中有先行词）
I don’t know where he came from.（宾语从句）
Where he has gone is not known yet.（主语从句）
This place is where they once hid.（表语从句）
练习、状语从句
一、用横线划出下列句子中的状语从句，并指出是哪种状语从句：
1. Child as she is, she knows a lot of things.
2. The more I can do for the class, the happier I’ll be.
3. He talks as if (as though) he knew all about it.
4. He is such a good teacher that the students love and respect him.
5.I shall go to the park unless it rains.
6. No sooner had I got home than it began to rain.
7. Where there is water, there is life.
8. He studied hard so that he could catch up with his classmates.
9. Since you are very busy, I won't trouble you.
10. Even if (though) I fail. I’ll never lose heart.
11. Once you begin the work, you must continue.
12. I will find her wherever she may be.
13. Now that you've come, you'd better have dinner with us.
14. He was so excited that he couldn't fall asleep.
15. We must do everything as he tells us.
16. India is much bigger than Japan.
17. No matter when you come, you are warmly welcome.
18. As (So) long as you work hard, you can catch up with the other classmat es.
状语从句（Adverbial Clause）状语从句指句子用作状语时，起副词作用的句子。

它可以修饰谓语、非谓语动词、定语、状语或整个句子。

根据其作用可分为时间、地点、原因、条件、目的、结果、让步、方式和比较等从句。

状语从句一般由连词(从属连词)引导，也可以由词组引起。

从句位于句首或句中时通常用逗号与主句隔开，位于句尾时可以不用逗号隔开。

状语从句的种类
状语从句可分为：
1.时间状语从句；(adverbial clause of time)
2.地点状语从句；(adverbial clause of place)
3.原因状语从句；(adverbial clause of cause)
4.条件状语从句；(adverbial clause of condition)
5.目的状语从句；(adverbial clause of purpose)
6.让步状语从句；(adverbial clause of concession)
7.比较状语从句；(adverbial clause of comparison)
8.方式状语从句；(adverbial clause of manner)
9.结果状语从句。

(adverbial clause of result)
[编辑本段]
状语从句的时态特点
一般情况下，时间和条件状语从句的谓语动词一般用“一般现在时”表示“一般将来时”，用“现在完成时”表示“将来完成时”。

例如：
I will call you as soon as I arrive in Beijing. 我一到北京就给你打电话。

（这是由as soon as引导的时间状语从句，从句中的谓语动词arrive是一般现在时，表示一般将来时，决不可用will arrive）
As soon as I have finished this work, I will go home. 我一完成此工作，就回家。

（从句中的谓语动词用现在完成时have finished，表示将来完成时,决不可用will have finished）
If he comes back, please let me know.如果他回来了，请通知我。

（从句中的谓语动词用comes back,表示一般将来时，决不可用will come back）状语从句讲解和练习
状语修饰动词、形容词、副词或整个句子。

通常由副词、介词短语、动词不定式、分词和从句等担当。

例如：
1. Naturally , our grandparents were pleased to get our phone call . (副词)
2. We worked hard , from sunrise to sunset . (介词状短语)
3. To help my disabled aunt , I spend an hour working in her house every day . (不定式)
4. Seen from a distance , the farmhouse looked deserted . (过去分词)
5. I know how to light a camp fire because I had done it before .（原因状语从句）
状语的位置比较灵活，可以位于句首、句末或句中。

enough用作状语修饰形容词和副词时必须后置。

状语从句主要用来修饰主句或主句的谓语。

一般可分为九大类，分别表示时间、地点、原因、目的、结果、条件、让步、比较和方式。

尽管种类较多，但由于状语从句与汉语结构和用法相似，所以理解和掌握它并不难。

状语从句的关键是要掌握引导不同状语从句的常用连接词
和特殊的连接词即考点。

现分别列举如下: 1．时间状语从句
常用引导词：when, as, while, as soon as, before, after, since , till, until 特殊引导词：the minute, the moment, the second, every time, the day，the instant, immediately , directly, no sooner … than, hardly …when, scarcely … when
I didn’t realize how special my mother was until I became an adult. While John was watching T V, his wife was cooking.
The children ran away from the orchard(果园), the moment they saw the guard.
No sooner had I arrived home ,then it began to rain. Every time I listen to your advice, I get int o trouble. 2．地点状语从句常用引导词：where
特殊引导词：wherever, anywhere, everywhere
Generally, air will be heavily polluted where there are factories. Wherever you go, you should work hard. 地点状语从句
§4地点状语从句 (adverbial clause of place)
地点状语从句一般由连接副词where, wherever等引导，已经形成了固定的句型，例如：句型1：Where＋地点从句，（there）＋主句。

【注意】此句型通常译成“哪里……哪里就……”；主句在从句后面时，there可用可不用；如果主句在从句的前面时，一般都不用there。

例如：
Where there is no rain, farming is difficult or impossible.在没有雨水的地方，耕作是困难的，或根本不可能的。

They were good persons. Where they went, there they were warmly welcomed. 他们都是好人。

因此他们走到哪里都受到热烈欢迎。

You should have put the book where you found it. 你本来应该把书放回原来的地方。

Where the Communist Party of China goes, there the people are liberated.哪里有了中国共产
党，哪里人民得解放。

句型2：Anywhere/ wherever＋地点从句，＋主句。

【注意】anywhere本身是个副词，但是，常可以引导从句，相当于连词，意思相似于wherever, anywhere引导的从句可位于主句之前，也可以位于主句之后。

而wherever本身就是个连词，表示“在何处，无论何处”。

例如： Wherever the sea is , you will find seamen.有海就有海员。

3 回答者：快乐如 3．原因状语从句
常用引导词：because, since, as, for
特殊引导词：seeing that, now that, in that, considering that, given that. My friends dislike me because I’m handsome and successful. Now that everybody has come, let’s begin our conference.
The higher income tax is harmful in that it may discourage people from trying to earn more.
Considering that he is no more than 12 years old, his height of 1.80 m is quite remarkable. 4．目的状语从句
常用引导词：so that, in order that
特殊引导词：lest, in case, for fear that，in the hope that, for the purpose that, to the end that The boss asked the secretary to hurry up with the letters so that he could sign them.
The teacher raised his voice on purpose that the students in the back could hear more clearly. 5．结果状语从句
常用引导词：so … that, such … that,
特殊引导词：such that, to the degree that, to the extent that, to such a degree that,
He got up so early that he caught the first bus. It’s such a good chance that we must not miss it .
To such a degree was he excited that he couldn’t sleep last night. 6．条件状语从句常用引导词：if, unless,
特殊引导词：as/so long as, only if, providing/provided that, supposing that, in case that, on condition that We’ll start our project if the president agrees.
You will certainly succeed so long as you keep on trying.
Provided that there is no opposition, we shall hold the meeting here. 7．让步状语从句
常用引导词：though, although, even if, even though
特殊引导词： as(用在让步状语从句中必须要倒装)，while ( 一般用在句首 )，no matter …， in spite of the fact that, while, whatever, whoever, wherever, whenever, however, whichever
Much as I respect him, I can’t agree to his proposal. 尽管我很尊敬他，我却不同意他的建议。

The old man always enjoys swimming even though the weather is rough.
No matter how hard he tried, she could not change her mind. He won’t listen whatever you may say. 8．比较状语从句
常用引导词：as(同级比较), than(不同程度的比较)
特殊引导词：the more … the more … ; just as …， so…; A is to B what /as X is to Y; no … more than; not A s o much as B She is as bad-tempered as her mother. The house is three times as big as ours. The more you exercise, the healthier you will be.
Food is to men what oil is to machine. 食物之于人，犹如油之于机器。

9．方式状语从句常用引导词：as, as if, how 特殊引导词：the way
When in Rome, do as the Roman do. She behaved as if she were the boss.
Sometimes we teach our children the way our parents have taught us. 10. 状语从句的简化♠状语从句的省略
状语从句同时具备下列两个条件:①主句和从句的主语一致，或从句主语为it；②从句主要动词是be的某种形式。

从句中的主语和be动词常可省略。

例如： When ( the museum is ) completed , the museum will be open to the public next year . He’ll go to the seaside for his holiday if (it is ) possible. 另外，比较状语从句经常省略。

例如： I’m taller than he (is tall ).
The higher the temperature (is), the greater the pressure (is ).
就状语从句而言,有时为了使语言言简意赅,常常将状语从句进行"简化"。

状语从句的"简化"现象在口语中较为普遍,而且在高考中的复现率也较高。

因此,有必要对其进行全面、透彻的了解。

状语从句的"简化"现象常存在于以下五种状语从句中:①由if, unless等引导的条件状语从句;
②由although, though, even if / though等引导的让步状语从句;③由when, while, as, before, after, until / till等引导的时间状语从句;④由as, as if等引导的方式状语从句;⑤由as, than等引导的比较状语从句。

下面针对这五种情形作一归纳。

(1)当状语从句的主语是it,且谓语动词是be时,it和be要完全简化掉。

例如: If (it is) possible, he will help you out of the difficulty.如果可能的话,他会帮你摆脱困境。

You must attend the meeting unless (it is) inconvenient to you.除非情况对你来说不方便,否则你必须出席这次会议。

(2)当状语从句的主语和主句的主语一致时,从句可以将主语和be动词简化掉。

常用于以下几种情形: a.连词+形容词
As (he was) young, he learned how to ride a bike.他小时候就学会了骑自行车。

Whenever (she is) free, she often goes shopping.她有空就去逛商店。

Work hard when (you are) young, or you'll regret.少壮不努力,老大徒伤悲。

b.连词+名词
While (he was) a young boy, he was always ready to help others.他在孩提时代就乐于助人。

Although (he was) a farmer, now he is a famous director.尽管他曾是个农民,而现在是位著名的导演了。

c.连词+现在分词
As (she was) walking along the river bank, she was singing a pop song.她沿着河堤边走边唱着流行歌曲。

Although (he is) doing his best in maths these days, he has still got no good marks.尽管近来他一直在学数学,但他仍然没有取得好成绩。

d.连词+过去分词
He won't go there with us unless (he is) invited.除非受到邀请,否则他不会和我们一道去那里。

The concert was a great success than (it was) expected.这场音乐会出乎意料地取得了巨大成功。

e.连词+不定式
He stood up as if (he were) to say something.当时他站起来好像要说什么。

He wouldn't solve the problem even if (he were) to take charge.即使他来负责,他也解决不了这个问题。

f. 连词+介词短语
She looked anxious as though (she was) in trouble.她看上去很焦急,好像遇到了麻烦。

He had mastered the English language before (he was) in the USA.他到美国之前就懂英语了。

注意:当从句主语和主句主语不一致时,从句部分要么用完全形式,要么用独立主格结构来表达。

例如:
When the meeting was over, all the people went out of the meeting-room.当会议结束时,人们都走出了会议室。

(=The meeting over,
[编辑本段] 一、时间状语从句
概念：在复合句中，由时间连接词引导的状语从句叫做时间状语从句。

(在复合句中，要注意主句和从句的时态大多都要保持一致。

）要点: 时间状语从句，由以下连词引导：
when while as after before as soon as since till /until by the time 在时间状语从句中，要注意时态一致。

一般情况下主句是将来时的时候，从句要用一般现在时。

1.when当...的时候
Mozart started writing music when he was four years old. (当)莫扎特4岁的时候，开始写音乐作品。

2.while当...时
He visited a lot of places while he was traveling. 他在旅途中参观了许多地方。

3.as在...的同时；一边...一边... He smiled as he stood up. 他一边站起来一边笑着。

4.after在...之后 He left the classroom after he had finished his homework the other day.
前几天做完作业之后回的家。

5.before 在...之前
Mr. Brown had worked in a bank for a year before he came here. 布朗先生来这之前已经在一家银行里工作一年了。

6.as soon as 一...就...
We began to work as soon as we got there. 我们一到那就开始工作。

I will write to you as soon as I get home. 我一到家就给你写信。

7.since 自。

以来到现在表示自过去的一个起点时间到目前(说话时间)为止的一段持续时间。

主句一般用现在完成时，从句用一般过去时。

Mr Green has taught in that school since he came to China three years ago.
自格林先生来中国以来，他就在这所学校教书。

(还可以用作介词，本句从句还可以用短语：since three years ago(自三年前以来)表示。

) 8 till /until
都可以作连词，连接时间状语，也可以作介词，与其它词构成介词短语，在句中作状语。

They walked till /until it was dark. 他们一直走到天黑。

Xiao Ming didn’t leave home till / until his father came back. 小明直到他爸爸回来才离开家。

9. by the time 到。

为止 (所在句子的主句应用完成时) By the time he gets there , his father has already gone. 他到家的时候，他爸爸已经走了。

By the time I got to school, the class had already began. 我到校时，已经开始上课了。

时间状语从句（adverbial clause of time）
1.由when, while, as引导的时间状语从句。

例如：
When you think you know nothing, then you begin to know something.当你以为自己一无所知的时候，你就是在开始知道一些事物了。

When truth is buried under the ground it grows, it chokes, it gathers such an explosive force that on the day it bursts out , it blows up everything with it.当真理被埋在地下的时候，它在生长，它感到压抑，它蓄存着这么一种爆炸性力量，一旦冒出，它就会炸破一切！ Strike while the iron is hot. 趁热打铁。

Will you watch my clothes while I have a swim. 我游泳的时候，请你照看一下我的衣服。

You can feel the air moving as your hand pushes through it. 当你的手在空气中挥动的时候，你就能感觉到空气在流动。

Our headmaster laughed as she spoke.我们的校长边谈边笑。

when, while和as的区别
when引导的从句的谓语动词可以是延续性的动词，又可以是瞬时动词。

并且when有时表示“就在那时”。

例如：
When she came in, I stopped eating.她进来时，我停止吃饭。

(瞬时动词) When I lived in the countryside, I used to carry some water for him.当我住在农村时，我常常为他担水。

（延续性的动词）
We were about to leave when he came in.我们就要离开，就在那时他进来了。

While引导的从句的谓语动词必须是延续性的，并强调主句和从句的动作同时发生（或者相对应）。

并且while有时还可以表示对比。

例如：
While my wife was reading the newspaper, I was watching TV. (was reading是延续性的动词，was reading和was watching同时发生)
I like playing football while you like playing basketball.我喜欢踢足球，而你喜欢打篮球。

（对比）
As表示“一边……一边”，as引导的动作是延续性的动作，一般用于主句和从句动作同时发生；as也可以强调“一先一后。

例如：
We always sing as we walk.我们总是边走边唱。

（as表示“一边……一边”） As we was going out, it began to snow.当我们出门时，开始下雪了。

（as强调句中两个动作紧接着先后发生，而不强调开始下雪的特定时间） as when while的辨析
as when while都表示主、从句动作同时发生，三者差异如下：表示“一边。

一边＂的意思
as 强调两个动作同时进行，并表示对比时用于发生时间较短时 when
1、还可以表示从句动词的动作在主几句动词的动作＂之前＂或＂之后＂发生。

2、when＝and then; at that moment (正在那个时候) while 1、用于时间较长时
2、强调两个动作同时进行，并表示对比时有时这三个连词可以互换，有时不可以。

lIt was raining hard when (as) I got there.
我到那里时，正在下大雨。

( 动作同时发生，when可换为as, 但不能换为while，因为get 是点动词.)
lWhen I had read the article, he called me.
我看完这篇文章之后，她给我打了电话。

( 从句动作发生在主句之前，注意时态表达，只能用when )
lWhen I got to the cinema, the film had begun.
(当)我到了电影院时，电影已经开演了。

(从句的动作发生在主句之后，只能用when,并要注意时态)
lHe was about to leave, when the telephone rang.
他正要离开，忽然电话响了。

( 此时不能放在句首。

主句动词一般表达“正在”“即将”. while, as不能代替
lShe thought I was talking about her daughter, while, in fact, I was talking about my daughter. 他以为我在谈她女儿，然而，实际上在谈论我女儿。

(表转折，对比，when, as都不能代替它)
lWhile the alien was buying a souvenir, the girl called the police. 外星人买纪念品时，那女孩给警察打了电话。

(表示主句，从句的动作同时发生，while后引导的状语从句的动词必须是延续动词不能是点动词，因为它表示较长时间)
lMother was worried because little Alice was ill, especially as (when/ while) father was away. 妈妈担心，因为小爱丽丝病了，特别是他父亲不在家的时候。

(此时as ,when, while可通用) 2.由before和after引导的时间状语从句。

注意before引导的从句不再用否定式的谓语，并且当before引导的从句位于主句之后，有时译成“就，才”。

还要注意主句和从句之间的时间关系。

当主句用将来时，从句总是用现在时；如果before引导的从句谓语用的是过去时，则主句动词多用过去完成时，这样以便体现动作发生的先后。

After表示主句动作发生在从句动作之后。

主句和从句的动作的时间关系正好与before引导的从句相反。

例如：
It will be four days before they come back. 他们要过四天才能回来。

Einstein almost knocked me down before he saw me.爱因斯坦几乎把我撞倒才看到我。

My father had left for Canada just before the letter arrived.我父亲恰好在信到之前去加拿大了。

They had not been married four months before they were divorced. 他们结婚还不到四个月就离婚了。

After you think it over, please let me know what you decide.你仔细考虑过以后，告诉我你是怎样决定的。

After we had finished the work, we went home.完成工作之后，我们回家了。

（从句用过去完成时，主句用一般过去时） 3.由till或until引导的时间状语从句。

till和until一般情况下两者可以互换，但是在强调句型中多用until。

并且要注意的是：如果主句中的谓语动词是瞬时动词时，必须用否定形式；如果主句中的谓语动词是延续性动词时，用肯定或否定形式都可以，但表达的意思不同。

例如： I didn't go to bed until （till） my father came back.直到我父亲回来我才上床睡觉。

It was not until the meeting was over that he began to teach me English.直到散会之后他才开始教我英语。

I worked until he came back.我工作到他回来为止。

I didn't work until he came back.他回来我这才开始工作。

Please wait until I arrived.在我到达之前请等我。

4.由since引导的时间状语从句。

since引导的从句的谓语动词可以是延续性的动词，又可以是瞬时动词。

一般情况下，从句谓语动词用一般过去时，而主句的谓语动词用现在完成时。

但在It is ＋时间＋since从句的句型中，主句多用一般现在时。

例如：
I have been in Beijing since you left. 自从你离开以来，我一直在北京了。

Where have you been since I last saw you? 自上次我和你见面以后，你到哪里去了？
It is four years since my sister lived in Beijing. 我妹妹不在北京住有四年了。

It is five months since our boss was in Beijing.我们老板离开北京有五个月了。

知识扩展
1. It is since从。

以来多长时间了(因为since +从句或名词，表示一段时间)
It is five years since we met last time.从我们上次见面已经五年了。

2. It is +before…(。

才) It was a long time before I went to sleep again. 过了很长时间我才睡着。

It was an hour before(＝until) the police arrived. 过了一个小时，警察才来。

5.由as soon as, immediately, directly, instantly, the moment, the instant, the minute, 等引导的时间状语从句。

这些连词都表示“一……就”。

例如： I will go there directly I have finished my breakfast. 吃完早饭，我立即到那里去。

The moment I heard the news, I hastened to the spot.我一听到消息，马上赶到了出事地点。

As soon as I reach Canada, I will ring you up. 我一到加拿大，就给你来电话。

我会去参加聚会的, 除非他也去.(如果他不去,我就去.) 4.You will be late unless you leave immediately.
如果你不马上走,你将会迟到的.(=If you don’t leave immediately, you will be late.)
难点提示：用条件状语从句时要注意时态的正确使用,当主句是将来时的时候,从句要用一般。