英語四級(jí)語法備戰(zhàn)-定語從句大全

18.6 as, which 非限定性定語從句

　　由as, which 引導(dǎo)的非限定性定語從句，as和which可代整個(gè)主句，相當(dāng)于and this或and that。As一般放在句首，which在句中。

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

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

典型例題　

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

A. it　 B. that　 C. which　　D. he

　 答案C. 此為非限定性從句，不能用 that修飾，而用which.，it 和he 都使后句成為句子，兩個(gè)獨(dú)立的句子不能單以逗號(hào)連接。況且選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，用于非限定性定語從句，而what不可。That 不能用于非限定性定語從句，it不為連詞，使由逗號(hào)連接的兩個(gè)句子并在一起在英語語法上行不通。

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在引導(dǎo)非限制性定語從句時(shí)，這兩個(gè)關(guān)系代詞都指主句所表達(dá)的整個(gè)意思，且在定語從句中都可以作主語和賓語。但不同之處主要有兩點(diǎn)：

　(1)as 引導(dǎo)的定語從句可置于句首，而which不可。

　(2) as 代表前面的整個(gè)主句并在從句中作主語時(shí)，從句中的謂語必須是系動(dòng)詞；若為行為動(dòng)詞，則從句中的關(guān)系代詞只能用which.。

　 在本題中，prevent由于是行為動(dòng)詞，所以正確選項(xiàng)應(yīng)為B。

As 的用法

例1. the same… as；such…as 中的as 是一種固定結(jié)構(gòu), 和……一樣……。

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

例2. as可引導(dǎo)非限制性從句，常帶有'正如'。

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

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

　As是關(guān)系代詞。例1中的as作know的賓語；例2中，它充當(dāng)從句的主語，謂語動(dòng)詞know要用被動(dòng)式。

18.7 先行詞和關(guān)系詞二合一

　1)Whoever spits in public will be punished here.

　　 (Whoever 可以用 anyone who 代替)

　2)The parents will use what they have to send their son to technical school.

　　(what 可以用all that代替)

18.8 what/whatever;that/what; who/whoever

1)what = the thing which；whatever = anything

　　　What you want has been sent here.

　　　Whatever you want makes no difference to me.

2) who= the person that　 whoever= anyone who

　　 （錯(cuò)）Who breaks the law will be punished.

　　 （錯(cuò)）Whoever robbed the bank is not clear.

　　 （對(duì)）Whoever breaks the law will be punished.

　　 （對(duì)）Who robbed the bank is not clear.

3) that 和 what　

　　當(dāng)that引導(dǎo)定語從句時(shí) ，通常用作關(guān)系代詞，而引導(dǎo)名詞性從句時(shí)，是個(gè)不充當(dāng)任何成分的連接詞。賓語從句和表語從句中的that常可省略。What只能引導(dǎo)名詞性從　句， 用作連接代詞，作從句的具體成分，且不能省略。

　　I think (that) you will like the stamps.

　　What we need is more practice.