wait. （05全国卷3）
A．in case B．so that C．in order
D．as if
In time of serious accidents, _____ we know some basic things about first aid, we can save lives.
A. whether B. until C. if D. unless (2010江西卷)—Our holiday costs a lot of money.
— Did it? Well, that doesn’t matter you enjoyed yourselves. A as long as
B unless
C as soon as D though 4. 原因状语从句
一、 for，because，since，as表示原因
for和because，since，as一样，都可作“因为”讲。但for不表示产生某种结果的必然因果关系，主从句之间用逗号隔开。because表示产生某种结果的必然因果关系，是全句的中心，主句反而成了次要的部分，有时主句甚至可以省略。回答why的问题只能用because．比较：
It must have rained last night，for the ground is wet． The ground is wet because it rained last night．
二、 since和as表示原因的份量不如because那么重，而且通常放在句首。如： Since you say so，I suppose it's true. As it is raining，I will not go out.
The day must be breaking, _____ the birds have begun singing.
A. because B. as C. for D. since
12年重庆卷30.—Coach, can I continue with the training?
—Sorry, you can’t ______you haven’t recovered from the knee injury. A. until B. before C. as D. unless 5. 目的状语从句
引导词： ① (so ) that; in order that (谓语常用can/ could/ may/ might/ will/ would
+ do); so as that
He wrote the words every other line _______they could appear clear.
The police officers in our city work hard __________ the rest of us can live a safe life.
Roses need special care ________ they can live through winter. ② for fear that = in case (以防)
Take an umbrella for fear that it (should) rain. Better take more clothes, in case it is cold today. 6. 结果状语从句
结果状语从句一般由so，so…that，such…that引导，放在主句之后。例如： The box is so heavy that nobody can move it. It is such a heavy box that nobody can move it. So heavy is the box that nobody can move it． 7. 方式状语从句
方式状语从句放在主句之后，用as，just as，as if, as though等引导。as if和as though引导的从句一般用虚拟语气。但如果从句中所陈述的情况很可能实现，也可用陈述语气。例如：
The old man runs very fast as if he were a young man. You may do as you please. Let’s study as Lei Feng studied. Think as I think.
He talks as if/though he is drunk. 8. 地点状语从句
地点状语从句常用where，wherever等连词引导。 Wherever you go，I'll follow you. Just stay where you are. 9. 比较状语从句
比较状语从句常由as…as，than，not so…as…，the more…the more等词引导。比较从句部分常是省略句。例如： I know you better than he does.
The more we can do for you, the happier we will be.
