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2008-11-02 23:56:42
一．as引导状语从句
as作为连词可以引导状语从句，表示时间、原因、方式、让步等。
1. 引导时间状语从句，意思是“当``````的时候”，同when/while,更强调“一边``````一边``````”。表“随着``````”的意思时同with,但with是介词，不可以跟从句。
eg: I saw him as he was getting off the bus.
He often listens to the music as he is doing his homework.
As time goes by, his illness is getting worse.
2. 引导原因状语从句，同since。
eg: We had better hurry as it is getting dark.
As she has no car, she can’t get there easily.
3. 引导让步状语从句，意思同though/although,但通常要用倒装结构。可以把从句中表语、状语甚至谓语动词置于句首，如果是带有冠词的可数名词单数作表语，置于句首时应省去冠词。
eg: Young as he is, he knows a lot about history.
Much as I like you, I will not marry you.
Try as she might, Mary couldn’t get the door open.
Boy as he is, he is very shy. (boy前省略冠词a)
4. 引导方式状语从句，表示方式。意思是“像，按照，如同”。
eg: Do it as I do it.
You should finish your task as you are told to.
Leave it as it is.
二．as引导定语从句
1. as引导限制性定语从句。
as作为关系代词可以引导限制性定语从句，通常与the same或such连用，构成the same
``````as和such``````as句型。
eg: I have never heard such stories as he tells.
This is the same dictionary as I lost.
2. as引导非限制性定语从句。
as与which一样都可以引导非限制性定语从句，但是as引导的从句可以放在主句之前、主句之后，甚至还可以分割主句；而which引导的非限制性定语从句只能放在主句之后。另外as还有“正如、就像”之意。
eg: As is mentioned above, the number of the students in senior high schools is increasing.
He was admitted to college, which made his parents very happy.
John, as you know, is a writer.
