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1. as作连词,引状从。
1)表"当......时候",引时状从,强调两个动作同时发生,或某事一发生,另一事立即发生。
如：She sang a song as she walked. 她边走边唱着一首歌。
2)表"因为"、"由于",引原状从，与because相近。
如：I must stop writing, as I have a lot of work to do. 我必须停笔,因为我有许多工作要做。
3)表"正如"、"按照""像......一样",引方式/比较状从。
如：Run as l do. (方状从)/My brother is as tall as I am. 我弟弟和我一样高。(比较状从)
4)as经常用在as... as possible结构中,表示"尽可能地......"。
如：as quickly as possible尽可能快,as much as possible尽可能多。
5)表"尽管"、"虽然",常用于倒装句式,引让步状从。
如： Old as he was, he still worked very hard. 他虽然年龄大了,但工作还很努力。
2. as用作介词，表"充当"、"作为"。
如：As a party member, I must be strict with myself. 作为一名党员,我必须严格要求自己。
She is famous as a singer. 她作为一名歌手而闻名。
3. as构成一些固定搭配。
1)as well as 同,和......一样;
如: My parents often go for a walk after supper as well as my brother. 我父母经常晚饭后散步,我哥哥也是。
2)as soon as 一......就......
如：I will call you as soon as I get to the station. 我一到车站就会给你打电话。
3)as long as 只要
如：As long asyou don't betray me, I'll do whatever you ask me to (do). 只要你不出卖我，要我做什么我都愿意。
As 用法专练
1.It is generally believed that teaching is ____ it is a science.
A. much as an art as B. as much an art as
C.an art as much as D.as much as an art
2. _____ I admire David as a poet,I don’t like him as a man.
A.Only if B.If only
C. As much D.Much as
3. ____ ,he talks a lot about his favourite singers after class.
A.A quiet student as he may be B.Quiet student as he may be
C.Quiet as he may be a student D.As he may be a quiet student
4.I wonder why you don’t do it as ____ and it’s the third time you have done so.
A.told you B. be told
C. told to D. you told
5.( 1) ___I explain on the phone,your request will be considered at the next meeting.
(2)____ I explain on the phone is that your request will be considered at the next meeting.
A. What B.When C.After D. As
6.(1)That is ____ problem____can’t be worked out by anyof us .
(2)That is ____problem____none of us can work it out.
A.a such difficult , that B.so difficult a ,that
C.such a difficult, as D.a so difficult ,as