【考点直击】
1. 时间状语从句
2. 条件状语从句
3. 原因状语从句
4. 结果状语从句
5. 比较状语从句
6. 目的状语从句
7. 让步状语从句
8. 地点状语从句
【名师点睛】
用来修饰主句中的动词，副词和形容词的从句叫状语从句。根据其含义状语从句可分为时间状语从句，地点状语从句，条件状语从句， 原因状语从句，结果状语从句，比较状语从句，目的状语从句，让步状语从句。
1. 时间状语从句
(1)时间状语从句常用when, as, while, before, after, since, till, until, as soon as等连词来引导。例如：
It was raining hard when got to school yesterday.
While he was doing his homework, the telephone rang.
As he walked along the lake, he sang happily.
He had learned a little Chinese before he came to China.
After he finished middle school, he went to work in a factory.
(2)在时间状语从句里，通常不用将来时态，用现在时态表示将来的动作或状态。例如：
I’ll ring you up as soon as I get to New York.
I will tell him everything when he comes back.
He won’t believe it until he sees it with his own eyes.
(3)在带有till或until引导的时间状语从句的主从复合句里，如果主句用肯定式，其含义是“一直到……时”，谓语动词只能用延续性动词。如果主句用否定式，其含义是“直到……才……”, “在……以前不……”, 谓语动词可用瞬间动词。例如：
The young man read till the light went out.
Let’s wait until the rain stops.
We won’t start until Bob comes.
Don’t get off until the bus stops.
2. 条件状语从句
(1)条件状语从句通常由if, unless引导。例如：
What shall we do if it snows tomorrow?
Don’t leave the building unless I tell you to.
(2)在条件状语从句里，谓语动词通常用现在时态表示将来的动作或状态。例如：
I’ll help you with your English if am free tomorrow.
He won’t be late unless he is ill.
(3)“祈使句 + and (or)+ 陈述句” 在意思上相当于一个带有条件状语从句的复合句。例如：
Hurry up, or you’ll be late.
=If you don’t hurry up, you’ll be late.
Study hard and you will pass the exam.
=If you study hard, you will pass the exam.
3. 原因状语从句
(1)原因状语从句通常由because, since, as引导。例如：
He didn’t come to school because he was ill.
As it is raining, we shall not go the zoo.
Since you can’t answer the question, I’ll ask someone else.
(2)because表示直接原因，语气最强。Because引导的原因状语从句多放在主句之后。回答由why提出的问题，只能用because。As和since语气较弱，一般用来表示明显的原因。由as和since引导的原因状语从居多放在句首。例如：
------Why aren’t going there?
------Because I don’t want to.
As he has no car, he can’t get there easily.
Since we have no money, we can’t buy it.
(3)because和so不能同用在一个句子里。
4. 结果状语从句
(1)结果状语从句由so…that, such…that, so that引导。例如：
He is so poor that he can’t buy a bike for his son.
She is such a good teacher that everybody likes her.
My pencil fell under the desk, so that I couldn’t see it.
(2)so…that语such...that可以互换。例如：
在由so...that引导的结果状语从句中，so是副词，与形容词连用。其结构是: “...so + 形容词（副词）+ that + 从句”。例如：
He was so glad that he couldn’t say a word.
The hall is so big that it can hold 2,000 people.
Mother lives so far away that we hardly ever see her.
在由such…that引导的结果状语从句中，such是形容词，它修饰的可以是单数或复数可数名词，也可以是不可数名词；名词前面可以带形容词，也可不带。如果是单数可数名词，前面需加不定冠词a或an。例如：
It was such a hot day that nobody wanted to do anything.
He had such long arms that he could almost touch the ceiling.
He made such rapid progress that he did very well in the mid-term.
      有时上述两种结构是可以互换的。例如：
It was such a wonderful film that all of us wanted to see it again.
=The film was so wonderful that all of us wanted to see it again.
It is such an important match that nobody wants to miss it.
=The match is so important that nobody wants to miss it.
(3)如果名词前由many, much, little, few等词修饰时，只能用so, 不用such。例如：
Soon there were so many deer that they ate up all the wild roses.
He has so little time that he can’t go to the cinema with you.
5. 比较状语从句
比较状语从句通常由as…as, 比较级 + than…等连词引导。例如：
Tom runs faster than John does.
This classroom is as big as that one.
6. 目的状语从句
(1)目的状语从句通常由 so that, in order that引导。例如：
We started early so that we could catch the first train.
He studies hard so that he could work better in the future.
We used the computer in order that we might save time.
(2)so that既可引导目的状语从句，又可引导结果状语从句。区别这两种从句的办法有两个：1)目的状语从句里往往带有情态动词can, could, may, might等。2)从意思上看，目的状语从句往往表示的目的很明确。例如：
Speak clearly so that they may understand you. (目的状语从句)
Jack is badly ill so that he has to rest.        (结果状语从句)
7. 让步状语从句
(1)让步状语从句通常由although, though等连词引导。例如：
Though he is young, he knows a lot.
Although I am tired, I must go on working.
(2)although(though)不能用在同一个句子中。例如：
我们不能说：Though it was raining hard, but he still went out.
应该说：Though it was raining hard, he still went out.或It was raining hard, but he still went out.
8. 地点状语从句
     地点状语从句常常由where来引导。例如：
     Go where you like.
     Where there is a will, there is a way.
【实例解析】
 1.You will stay healthy _______ you do more exercise, such as running and walking.
  A. if  B. how  C. before  D. where
  答案：A。该题考查的是引导状语从句的从属连词的选择。从意思上看，从句应是一个条件状语从句，在这四个选项中只有if能引导条件状语从句，所以选A。
 2. ---Shall we go on working?
  ---Yes, _________ I prefer to have a rest.
  A. when  B. if  C. because  D. though
  答案：D。该题考查的是引导状语从句的从属连词的选择。从意思上看，只有选though才能说得通。
  3.None of us knew what had happened _________  they told us about it.
  A. when  B. until  C. after  D. though
  答案：B。该题考查的是引导状语从句的从属连词选择。本句的意思是“在……以前我们没人知道这件事。”要表达着一意思应用“not…until” 这一句型。
  4.---I hope you’ll enjoy your trip, dear!
  ---Thank you, mum. I’ll give you a call _________ I get there.
  A. until  B. as soon as  C. since  D. till
  答案：B。该题考查的是引导状语从句的从属连词的选择。本题的意思是“一到那里，我就给你打电话。”要表达这个意思应选用as soon as。