今天给大家讲一个SAT语法中的比较常见的也是必考的知识点——状语从句。状语从句又是复合句的一种，所以想了解复合句的小伙伴们也可以点击链接去学习~
地点状语从句
地点状语从句通常由where, wherever 引导。
Where I live there are plenty of trees.
Wherever I am I will be thinking of you.
方式状语从句
方式状语从句通常由as, (just) as…so…, as if, as though引导。
1) as, (just) as…so…引导的方式状语从句通常位于主句后，但在(just) as…so…结构中位于句首，这时as从句带有比喻的含义，意思是"正如…"，"就像"，多用于正式文体，例如：
Always do to the others as you would be done by.
你希望人家怎样待你，你就要怎样待人。
As water is to fish, so air is to man.
我们离不开空气，犹如鱼儿离不开水。
Just as we sweep our rooms, so we should sweep backward ideas from our minds.
正如打扫房屋一样，我们也要扫除我们头脑中落后的东西。
2) as if, as though两者的意义和用法相同，引出的状语从句谓语多用虚拟语气，表示与事实相反，有时也用陈述语气，表示所说情况是事实或实现的可能性较大。汉译常作"仿佛……似的"，"好像……似的"，例如：
They completely ignore these facts as if (as though) they never existed.
他们完全忽略了这些事实，就仿佛它不存在似的。(与事实相反，谓语用虚拟语气。)
He looks as if (as though) he had been hit by lighting.
他那样子就像被雷击了似的。(与事实相反，谓语用虚拟语气。)
It looks as if the weather may pick up very soon.
看来天气很快就会好起来。(实现的可能性较大，谓语用陈述语气。)
说明：as if / as though也可以引导一个分词短语、不定式短语或无动词短语，例如：
He stared at me as if seeing me for first time.
他目不转睛地看着我，就像第一次看见我似的。
He cleared his throat as if to say something.
他清了清嗓子，像要说什么似的。
比较：because, since, as和for
1) because语势最强，用来说明人所不知的原因，回答why提出的问题。当原因是显而易见的或已为人们所知，就用as或 since。
I didn't go, because I was afraid.
Since /As the weather is so bad, we have to delay our journey.
2) 由because引导的从句如果放在句末，且前面有逗 号，则可以用for来代替。但如果不是说明直接原因，而是多种情况加以推断，就只能用for。
He is absent today, because / for he is ill.
He must be ill, for he is absent today.
表示目的状语的从句可以由that, so that, in order that, in case等词引导，例如：
You must speak louder so that /in order that you can be heard by all.
Better take more clothes in case the weather is cold.
结果状语从句常由so… that 或 such…that引导，掌握这两个句型，首先要了解so 和 such与其后的词的搭配规律。
比较：so和 such
其规律由so与such的不同词性决定。such 是形容词，修饰名词或名词词组，so 是副词，只能修饰形容词或副词。 so 还可与表示数量的形容词many, few, much, little连用，形成固定搭配。
so foolish, such a fool
so nice a flower, such a nice flower
so many / few flowers, such nice flowers
so much / little money, such rapid progress
so many people, such a lot of people ( so many 已成固定搭配，a lot of 虽相当于 many，但 a lot of 为名词性的，只能用such搭配。)
so…that与such…that之间的转换既为 so与such之间的转换。
The boy is so young that he can't go to school.
He is such a young boy that he can't go to school
连接词主要有 if, unless, as/so long as, on condition that 等。.
if 引导的条件句有真实条件句和非真实条件句两种。非真实条件句已在虚拟语气中阐述。
unless = if not.
Let's go out for a walk unless you are too tired.
If you are not too tired, let's go out for a walk.
though, although
注意： 当有though, although时，后面的从句不能有but，但是 though 和yet可连用
Although it's raining, they are still working in the field.
ever if, even though. 即使
We'll make a trip even though the weather is bad.
whether…or- 不管……都
Whether you believe it or not, it is true.
"no matter +疑问词" 或"疑问词+后缀ever"
No matter what happened, he would not mind.
Whatever happened, he would not mind.
替换：
no matter what = whatever
no matter who = whoever
no matter when = whenever
no matter where = wherever
no matter which = whichever
no matter how = however
注意：no matter 不能引导主语从句和宾语从句。
比较while, when, as
1)as, when 引导短暂性动作的动词。
Just as / Just when / When I stopped my car, a man came up to me.
2)当从句的动作发生于主句动作之前，只能用when 引导这个从句，不可用as 或 while。
When you have finished your work, you may have a rest.
3)从句表示"随时间推移"连词能用as，不用when 或while。
As the day went on, the weather got worse.
日子一天天过去，天气越变越坏。
比较until和till
此两个连词意义相同。肯定形式表示的意思是"做某事直至某时"，动词必须是延续性的。否定形式表达的意思是"直至某时才做某事"。动词为延续性或非延续性都可 以。 正确使用这两个连词的关键之一就在于判断句中的动词该用肯定式还是否定式。
1)Until可用于句首，而till通常不用于句首。
Until you told me, I had heard nothing of what happened.
直到你告诉我以前，出了什么事我一点也不知道。
2)Until when 疑问句中，until要放在句首。
Until when are you staying? 你呆到什么时候?
Until next Monday. 呆到下周一。
注意：否定句可用另外两种句式表示。
3)Not until …在句首，主句用倒装。
Not until the early years of the 19th century did man know what heat is.
直到19 世纪初，人类才知道热能是什么。
Not until I began to work did I realize how much time I had wasted.
直到我开始工作，我才认识到了我已蹉跎了几多岁月。
4) It is not until… that… 表示"一…就…"的结构
hardly/scarcely…when/before, no sooner…than 和as soon as都可以表示"一…就…"的意思，例：
I had hardly / scarcely got home when it began to rain.
I had no sooner got home than it began to rain.
As soon as I got home, it began to rain.
注意：如果hardly, scarcely 或no sooner置于句首，句子必须用倒装结构：
Hardly / Scarcely had I got home when it began to rain.
No sooner had I got home than it began to rain.
