As we know, smoking is harmful to one's health.+ X6 s: i7 R2 e) f* o: L
The sun heats the earth, which is very important to us.1 {8 |. O2 F \' R
典型例题
$ t. `3 Q$ \& ]8 [8 H; Y 1)Alice received an invitation from her boss, ___came as a surprise.
8 ^# U3 i; Z, Q* A. o2 c A. it B. that C. which D. he
1 Z8 D7 A h4 o5 X! L2 v7 I; T 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。
) \( C, `$ \. r+ U5 ~' V' o 2)The weather turned out to be very good, ___ was more than we could expect.
0 g9 p1 _ X7 B8 J A. what B. which C. that D. it- M3 v) n2 |$ d( s
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。. y: {0 N3 q& G/ u- [* r/ q
3)It rained hard yesterday, ____ prevented me from going to the park..
9 {7 r2 N% T( a A. that B. which C. as D. it
4 Q& ~: c& C: z$ ^4 w 答案B.
4 Q& Y! s# v1 x& ]6 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:% L: C9 W9 Q" G2 e) q( e& C
(1) as 引导的定语从句可置于句首,而which不可。. R F8 Z# U; N4 }* x
(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.。& R, l: r9 O. s) {7 r
在本题中,prevent由于是行为动词,所以正确选项应为B。
% J" s% h0 s$ J' A0 A1 j As 的用法/ ^- H5 }* t0 C6 u1 g
例1. the same… as;such…as 中的as 是一种固定结构, 和……一样……。
* V8 l& |7 ^. r% p' D5 o I have got into the same trouble as he (has).
4 b, @ W7 K# }& N8 H9 {# o. P 例2. as可引导非限制性从句,常带有'正如'。, p" _* [ q1 q
As we know, smoking is harmful to one's health.
$ z/ U- j' i8 y2 ^7 c; _% Z) l As is know, smoking is harmful to one's health.+ u) }$ j. z6 [( @3 f
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。 |