as和which用法的区别?

如题所述

区别:
1)as可指其前后主句提到的事实或情况,因此引导的非限制性从句位置比较灵活,which可以放在主句前后,也可插入主句之中;而which引导的非限制性从句只能位于主句之后:
As is known to all, fish can’t live without water.
Air, as we know, is gas.

2)在非限制性从句中,which后的be动词不可省;as而后的be动词可以省略:
She told me she won the match , which was a lie. The material is elastic, as (was) shown in the figure.

3) which在非限制性定语从句做主语时可用各类动词做谓语;而在非限制性定语从句做主语时,谓语常用连系动词,如be, seem, become等,一般不用其他行为动词:
He saw the girl, which delighted him.
He didn’t say anything at the meeting , as/which seemed very strange.

4) 如果主句中叙述的事情与从句所涉及的意向一致,多用as,用以对主句的意义进行补充;如果不一致,就用which:
She has married again, as was expected.
He broke the rules again, which was unexpected.

5)如表示“如同。。。那样,按照,正如”含义,常用as,这里as主要起与上下文联系的作用,表达说话人的看法,并指出内容,出处和根据等,常用的结构有as we know(众所周知)as often happens(正如常发生的那样)as is often the case(情况常常如此)as we all can see(正如我们看到的)
be+announced/expected/known/imagined/mentioned/said/shown/reported(正如所。。。)等。这些结构常放句首,偶尔也可以放句中或句末 :
As is known to all, China is a developing country. Kate was late for school , as often happened.

6)在非限制性定语从句中关系代词指代主句中某一个单词时,常用which:
My brother enjoyed playing basketball , which he really plays well. Beijing , which he was born in, is our capital.

7)在非限制性定语从句中“介词+关系代词(介宾代物)”中关系代词只能用which :
The Travel Agency, with which our company has been dealing for several
years, has opened for new branches
Air is a mixture of gases, of which oxgen forms 21 percent.

8)有时用case, point, time, situation或reason等抽象名词来总结主句的内容,可用“介词+ which +抽象名词”构成从句 :
Ten years of hard work changed her greatly , for which reason he could hardly recognise her at first sight.
The machine may be out of order , in which case it will be repaired at once.

9)在非限制性定语从句关系代词用以代表主句中谓语的整个概念,从句中的谓语动词是否定形式时,常用which:
He can write a letter in English, which I can not.
Metal will bear beating with a hammer, which a stone willl not

10)在非限制性定语从句关系代词代表前面主句中的宾语从句时,常用which :
He said he had passed the exam , which was untrue.
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