教学过程一、复习预习定语从句是由关系代词或关系副词引导的从句，其作用是作定语修饰主句的某个名词性成分，相当于形容词，所以又称为形容词性从句，一般紧跟在它所修饰的先行词后面。

定语从句又分为限制性定语从句和非限制性定语从句。

限制性定语从句对被修饰的先行词有限定制约作用，使该词的含义更具体，更明确。

限制性定语从句不能被省略，否则句意就不完整。

非限制性定语从句与先行词关系不十分密切，只是对其作一些附加说明，不起限定制约作用。

如果将非限制性定语从句省去，主句的意义仍然完整。

本节我们着重研究限定性定语从句。

二、知识讲解非限制性定语从句：从句和先行词关系不密切，去掉定从句，意思仍然完整。

形式上用逗号隔开，不能that用引导。

e.g. Tom’s father, who is over sixty, still works hard day and night.（who引导非限制性定语从句，整个句子可分成两句来翻译）考点/易错点1非限定性定语从句中which和as均可使用，一般情况下，逗号后which表示预料之外的事情，而逗号后的as则表示预料之内的事情，e.g.He didn’t come, which surprised u s.他没有来，我们非常吃惊；He didn’t come, as we had expected.他没有来，正如我们所料。

考点/易错点2which可以在特殊定语从句中作定语，修饰fact, matter, thing 等名词。

这些名词代表先行成分表达的意义，有时将其略去句义仍然完整。

as不能作定语。

如：I was told to go not by train but bus, which advice I followed.考点/易错点3同时注意一个问题，限定性和非限定性定语从句在语义上有时略有差别：There are 5 people, who were injured in the accident.（表示共5个人）There are 5 people who were injured in the accident.（表示人很多，但受伤的只有5个）He didn’t wear clothes which will distinguish him from others.他不穿那些会把他和别人分开的衣服。

（他不穿奇装异服）He didn’t wear clothes,which will distinguish him from others.他不穿衣服，这把他和别人分开。

造成这样歧义的原因就在于逗号的which课表示前文整句话。

考点/易错点4as引导定语从句时的用法①as引导限制性定语从句通常用于the same … as, such … as结构中。

e.g. I want the same shirt as my friend’s. 我要一件跟我朋友一样的衬衫。

Such machines as are used in our workshop are made in China. 我们车间使用的这种机器是中国制造的。

②as引导非限制性定语从句既可放在主句之前，也可放在主句之后，用来修饰整个句子。

通常用下列句型：as is known to all, as is said, as is reported, as is announced, as we all know, as I expect 等。

e.g. As I expected, he got the first place again in this mid-term examination. 正如我所预料的那样，他在这次期中考试中又获得了第一名。

3）as 引导非限制性定语从句时与which的区别①当主句和从句语义一致时，用as；反之，用which来引导非限制性定语从句。

e.g. He made a long speech, as we expected.He made a long speech, which was unexpected.②当非限制定语从句为否定时，常用which引导。

e.g. Tom drinks a lot every day, which his wife doesn’t like at all.三、例题精析【例题1】【题干】___________ is known to everybody, the noon travels around the earth once every month.(NMET 2001)A.ItB.AsC.ThatD.What解析：答案为B。

本题考查as引导的非限制定语从句。

as作“正如……”解时，引导的非限制性定语从句来修饰整个句子。

当as在从句中作主语时，常用于下列短语：as is known、as is said、as is reported、as is announced等。

要注意掌握作关系代词引导定语从句的用法。

【答案】B【解析】本题考查as引导的非限制定语从句。

as作“正如……”解时，引导的非限制性定语从句来修饰整个句子。

当as在从句中作主语时，常用于下列短语：as is known、as is said、as is reported、as is announced等。

要注意掌握作关系代词引导定语从句的用法。

【例题2】【题干】3. _____ is known to everybody, the moon travels round the earth once every month.A. ItB. AsC. ThatD. What【答案】B【解析】【容易误选A，认为此处应填一个形式主语。

【分析】最佳答案是B。

as 引导的是一个非限制性定语从句。

比较下面一题：_______ is known to everybody that the moon travels round the earth once every month.A. ItB. AsC. ThatD. What此题答案选A，it 为形式主语，真正的主语是后面的that 从句【例题3】【题干】He had thousands of students, many of ______ gained great success in their own field.A. whomB. themC. whichD. who【答案】A【解析】【陷阱】容易误选B，用them 代指students.【分析】最佳答案是A，many of whom gained great success in their own field 为非限制性定语从句。

假若在many of... 的前面加上连词and，则选答案B。

四、课堂运用【基础】On Sundays there were a lot of children playing in the park, _______ parents seated together joking.A. theirB. whoseC. whichD. that答案A 容易误选B，认为这是非限制性定语从句。

解析their parents seated together joking 不是非限制性定语从句，而是一个独立主格结构，因为空格后的动词seated 不是谓语，而是一个过去分词，因为seat 作动词用时，是及物动词。

比较以下相似题：（1）On Sundays there were a lot of children playing in the park, _______ parents were seated together joking.A. theirB. whoseC. whichD. that选B.whose parents were seated together joking 为非限制性定语从句，因为其后有完整的谓语were seated.（2）On Sundays there were a lot of children playing in the park, and _______ parents were seated together joking.A. theirB. whoseC. whichD. that选A.因为句中有并列连词and，整个句子为并列句。

（3）On Sundays there were a lot of children playing in the park, _______ parents sitting together joking.A. theirB. whoseC. whichD. that选A.their parents sitting together joking 为独立主格结构。

（4）On Sundays there were a lot of children playing in the park, _______ parents sat together joking.A. theirB. whoseC. whichD. that选B.whose parents sat together joking 为非限制性定语从句，因为句中有完整的谓语sat.（5）On Sundays there were a lot of children playing in the park, _______ parents were sitting together joking.A. theirB. whoseC. whichD. that选B.whose parents were sitting together joking 为非限制性定语从句，因为句中有完整的谓语were sitting.【巩固】If the man is only interested in your looks, _____ just shows how shallow he is.A. asB. whichC. whatD. that【陷阱】容易误选A或B，误这是非限制性定语从句。

【分析】正确答案为D，注意逗号前是一个条件状语从句，逗号后是该状语从句的主句，that 在此代表前文所述的情况，用作主句的主语。

【拔高】The buses, most of _______ were already full, were surrounded by an angry crowd.A. thatB. itC. themD. which【陷阱】容易误选C，用them 代指the buses.【分析】最佳答案是D。