成三英语:as,which非限定性定语从句详解

2011-10-31 00:00:00来源:新东方论坛

As we know, smoking is harmful to one's health.

The sun heats the earth, which is very important to us.

典型例题

1)Alice received an invitation from her boss, ___came as a surprise.

A. it B. that C. which D. he

答案C. 此为非限定性从句,不能用 that修饰,而用which.,it 和he 都使后句成为句子,两个独立的句子不能单以逗号连接。况且选he句意不通。

2)The weather turned out to be very good, ___ was more than we could expect.

A. what B. which C. that D. it

答案B.which可代替句子,用于非限定性定语从句,而what不可。That 不能用于非限定性定语从句,it不为连词,使由逗号连接的两个句子并在一起在英语语法上行不通。

3)It rained hard yesterday, ____ prevented me from going to the park……

A. that B. which C. as D. it

答案B.

as 和which在引导非限制性定语从句时,这两个关系代词都指主句所表达的整个意思,且在定语从句中都可以作主语和宾语。但不同之处主要有两点:

(1) as 引导的定语从句可置于句首,而which不可。

(2) as 代表前面的整个主句并在从句中作主语时,从句中的谓语必须是系动词;若为行为动词,则从句中的关系代词只能用which.。

在本题中,prevent由于是行为动词,所以正确选项应为B.

As 的用法

例1. the same… as;such…as 中的as 是一种固定结构, 和……一样……。

I have got into the same trouble as he (has)。

例2. as可引导非限制性从句,常带有'正如'.

As we know, smoking is harmful to one's health.

As is know, smoking is harmful to one's health.

As是关系代词。例1中的as作know的宾语;例2中,它充当从句的主语,谓语动词know要用被动式。

本文关键字: 考试

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