导入练习11. —Is that the small company you often refer to?—Right, just the one _______ you know my father used to work for years.A.thatB. whichC. whereD. As2. —Where did they fi nish the experiment?—It was in the lab _______ was taken charge of by Prof. Smith.A. whereB. /C. whichD. in which3. Examination compositions, together with most business letters and government reports, are the main situations _______ formal language is used.A. in whichB. in thatC. of whichD. of that4. Which fi lm is the one _______ main actor has won the Best Actor Prize in the fi lm festival?A. whoB. whomC. whoseD. which5. In that country, November 30th is a national festival _______ everyone, men and women, old and young, sings and dances happily in the streets.A. whereB. whenC. thatD. as6. This is John Brown, _______ I think has something interesting to tell you.A. whichB. whomC. thatD. who7. We climbed the Huangshan Mountain yesterday, _______, not surprisingly, was crowded with visitors from all over the world.A. whereB. whichC. thatD. when8. The famous football player, _______ a big party will be held tomorrow morning, is to arrive this afternoon.A. in honour of himB. in his honourC. in whose honourD. in which honour9. _______ was reported in the newspaper, seventeen passengers had been killed in the traffi c accident.A. ItB. AsC. WhatD. That10. The owner paid the worker $10 for tidying the whole building, most of _______ hadn’t been cleaned for at least a year.A. thatB. whatC. whenD. which11. He has made great contributions to the science of physics, _______ he was awarded the 2009 Nobel Prize.A. about whichB. whatC. for whichD. when12. I don’t want to use the same tool _______ you used yesterday to repair the air conditioner.A. itB. thatC. oneD. what13. They were interested _______ you told them.A. in whichB. in thatC. all thatD. in everything14. Is that the reason _______ you are in favor of the proposal?A. whichB. whatC. whyD. for that15. I have bought the same dress _______ she is wearing.A. asB. thatC. whichD. what限制性定语从句提供有关主语或宾语的重要信息，起限定作用，与被修饰部分的关系紧密，如果省略该从句会使主句语义表达不完整。
例如：This is the very person that is wanted by the police.He is the man who /that lives next door.非限制性定语从句只是用来对被修饰部分作补充性的说明，与先行词关系比较松散，先行词与从句间可以用逗号隔开，从句可略去：The minister, who is to visit our university, is said to be a Qinghua University graduate.The businessman, whose suitcase has been found by a stranger, has left for Beijing.如果定语从句的先行词是专有名词或是带有形容词性物主代词(my, his, etc)或形容词性指示代词(this, that, etc)作限定词的名词词组，其后的定语从句通常为非限制性的。
例如：My mother, who has been on a visit to Australia, will fly back tomorrow..限制性定语从句的先行词只能是名词，代词或名词性词组，而非限制性定语从句的先行词除了是名词及名词性词组外，还可能是句子的一部分或是整个句子。
例如：They say he plays truant, which he doesn’t. [which指代plays truant]The meeting was put off till next month, as we hoped. [as指前面的句子]下面的表格归纳了前面已提到的两者不同之处：表一：限制性定语从句与非限制性定语从句的区别限制性定语从句非限制性定语从句1．提供确定或限定主句中某个名词的信息。
1．提供对确定主句中某个名词的非主要附加信息。
2．由深层嵌入句派生而来。
2．由两个独立的深层嵌入句派生而来。
3．无分隔定语从句和主句和停顿或特殊标点符号（逗号/插入语/破折号）。
3．书面语中用逗号，口语中用特殊的停顿和降低声调来把定语从句和主句分隔开来。
4．不可以修饰整个命题，只修饰一个名词。
4．可以修饰一个中心名词，或以评价的形式修饰整个命题。
5．可使用that和who(m),which等关系代词。
5．That不能当作关系代词，只可用wh-代词。
6．不常用来修饰专有名词。
6．既可修饰普通名词，也可修饰专有名词。
7．可修饰带有any 或every等类属限定词的中心名词。
7．不可修饰带有any 或every等类属限定词的中心名词。
as的用法1、as引导限制性定语从句时，常与such或the same连用，构成the same…as; such…as结构，as用于代替指人或物的先行词。
例如：I have never eaten such tasty foods as she cooked me.试比较the same…as和the same…that：This is the same book as I read last week.（这和我上周读的那本书是一样的。
）This is the same book that I read last year.（这就是我上周读的那本书。
）如果先行词表示抽象概念，则没有这种区别，例如：She told me the same story as/that she had told you.在as／so…as结构中，后面的as也是关系代词，例如：We took as many men as could be permitted to attend the meeting.2、引导非限制性定语从句关系代词as引导非限制性定语从句时，用于代替整个主句，意思是“正如”，相当于and this或and that。
as从句位置较之which引导的非限制性定语从句更加灵活，因而as从句既可以指前面提到的内容，也可以指后面将要提到的内容，which一般在主句后。
例如：The test is cancelled, as you have hoped.The test, as you have hoped, is cancelled.▲注：as代表前面的整个主句并在从句中做主语时表达的意思应与主句一致，而且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.例如：He failed to pass the exam again, as is predicted.He failed to pass the exam again, which annoyed his mother greatly.记住以下的as结构：as is known to all (众所周知)，as is often the case (情况常常如此)，as the name Indicates／suggests (顾名思义)，as may be imagined (可以想象得出)，as often happens (这种情况常常发生)，as has been said before (如前所述)，as has been pointed out (正如已经指出的)，as will be shown in ( 将在…中指出)，as is hoped ( 正如所希望的)3 介词+ 关系代词“介词+ 关系代词”引导的定语从句既可以是限制性定语从句，又可以是非限制性定语从句，“介词+关系代词”在从句中做主语、宾语、状语、定语等，介词的选择则要根据它与其先行词的关系或前后名词、动词等的搭配关系来决定，同时还应该考虑句子在上下文中要表达的意思。