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语法(从句)

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什么是表语从句,什么是定语从句?
解题思路: 所谓从句,就是一个主谓结构相当于整个句子(这样的句子叫复合句)的一个成分,因此,从句不能单独使用。在复合句中修饰名词或代词、作定语的句子叫定语从句。定语从句是中国人学英语的难点之一。
解题过程:
表语从句
表语从句于主句中的系动词之后,主要有四类:

1)由连词who, what, which 等引导的表语从句。这些词不但可以起连接作用,还可以在句中做主语、宾语和表语。
例如:
What concerns me most is who will be my teacher next term.
我最关心的是下一学期谁会做我们的老师。
China is not what she was yesterday.
中国已不再是以前的那个中国了。

2)由不充当任何句子成分的连词that, whether引起的表语从句。
例如:
What I mean is that we should help each other.
我的意思是我们应该互相帮助。
The problem is whether we can finish the work on time.
问题是我们能不能按时完成工作。

3)由连接副词when, where , why , how 引导的表语从句。
例如:
This is when I really get to know Americans.
我这时才开始认识美国人。
The question under discussion is where we will hold the meeting .
现在正讨论的问题是会议该在哪里举行。

4)由连词as, because, as if, as though 引导的表语从句。
例如:
It looks as if it is going to rain tonight.
看起来好像今晚要下雨。
The mistake happened because we are careless.
我们之所以犯错误是因为我们太粗心。
定语从句
在复合句中,修饰某一名词或代词的从句叫做定语从句。在定语从句中,被修饰的这一名词或代词叫做先行词。在定语从句中的引导词叫做关系词。关系词又分关系代词和关系副词。
关系代词有:who, whom, whose, that, which等。
关系副词有:when, where, why等。

关系代词所代替的先行词是人或物的名词或代词,并在句中充当主语、宾语、定语等成分。关系代词在定语从句中作主语时,从句谓语动词的人称和数要和先行词保持一致。
1)who, whom, that
这些词代替的先行词是人的名词或代词,在从句中所起作用如下:
Is he the man who/that wants to see you?
他就是你想见的人吗?(who/that在从句中作主语)
He is the man whom/ that I saw yesterday.
他就是我昨天见的那个人。(whom/that在从句中作宾语)

2) Whose 用来指人或物,(只用作定语, 若指物,它还可以同of which互换), 例如:
They rushed over to help the man whose car had broken down. 那人车坏了,大家都跑过去帮忙。
Please pass me the book whose (of which) cover is green. 请递给我那本绿皮的书。

3)which, that
它们所代替的先行词是事物的名词或代词,在从句中可作主语、宾语等,例如:
A prosperity which / that had never been seen before appears in the countryside. 农村出现了前所未有的繁荣。(which / that在句中作主语)
The package (which / that) you are carrying is about to come unwrapped. 你拿的包快散了。(which / that在句中作宾语)

关系副词可代替的先行词是时间、地点或理由的名词,在从句中作状语。
1)when, where, why
关系副词when, where, why的含义相当于"介词+ which"结构,因此常常和"介词+ which"结构交替使用,例如:
There are occasions when (on which) one must yield. 任何人都有不得不屈服的时候。
Beijing is the place where (in which) I was born. 北京是我的出生地。
Is this the reason why (for which) he refused our offer? 这就是他拒绝我们帮助他的理由吗?

2)that代替关系副词
that可以用于表示时间、地点、方式、理由的名词后取代when, where, why和"介词+ which"引导的定语从句,在口语中that常被省略,例如:
His father died the year (that / when / in which) he was born. 他父亲在他出生那年逝世了。
He is unlikely to find the place (that / where / in which) he lived forty years ago. 他不大可能找到他四十年前居住过的地方。

·判断关系代词与关系副词
方法一: 用关系代词,还是关系副词完全取决于从句中的谓语动词。及物动词后面无宾语,就必须要求用关系代词;而不及物动词则要求用关系副词。例如:
This is the mountain village where I stayed last year.
I'll never forget the days when I worked together with you.

判断改错(注:先显示题,再显示答案,横线;用不同的颜色表示出。)
(错) This is the mountain village where I visited last year.
(错) I will never forget the days when I spent in the countryside.
(对) This is the mountain village (which) I visited last year.
(对) I'll never forget the days (which) I spent in the countryside.

习惯上总把表地点或时间的名词与关系副词 where, when联系在一起。此两题错在关系词的误用上。

方法二: 准确判断先行词在定语从句中的成分(主、谓、宾、定、状),也能正确选择出关系代词/关系副词。
例1. Is this museum ___ you visited a few days age?
A. where B. that C. on which D. the one
例2. Is this the museum ____ the exhibition was held.
A. where B. that C. on which D. the one
答案:例1 D,例2 A

例1变为肯定句: This museum is ___ you visited a few days ago.
例2变为肯定句: This is the museum ___ the exhibition was held.
在句1中,所缺部分为宾语,而where, that, on which都不能起到宾语的作用,只有the one既做了主句的表语,又可做从句的宾语,可以省略关系代词,所以应选D。
而句2中, 主、谓、宾俱全,从句部分为句子的状语表地点,既可用副词where,又因 in the museum词组,可用介词in + which 引导地点状语。而此题中,介词on 用的不对,所以选A。
关系词的选择依据在从句中所做的成分,先行词在从句中做主、定、宾语时,选择关系代词 (who, whom, that, which, whose); 先行词在从句中做状语时,应选择关系副词 ( where 地点状语,when 时间状语,why 原因状语) 。

1) 定语从句有限制性和非限制性两种。限制性定语从句是先行词不可缺少的部分,去掉它主句意思往往不明确;非限制性定语从句是先行词的附加说明,去掉了也不会影响主句的意思,它与主句之间通常用逗号分开,例如:
This is the house which we bought last month. 这是我们上个月买的那幢房子。(限制性)
The house, which we bought last month, is very nice.这幢房子很漂亮,是我们上个月买的。(非限制性)
2) 当先行词是专有名词或物主代词和指示代词所修饰时,其后的定语从句通常是非限制性的,例如:
Charles Smith, who was my former teacher, retired last year. 查理·史密斯去年退休了,他曾经是我的老师。
My house, which I bought last year, has got a lovely garden. 我去年买的的那幢房子带着个漂亮的花园。
This novel, which I have read three times, is very touching. 这本小说很动人,我已经读了三遍。

3) 非限制性定语从句还能将整个主句作为先行词, 对其进行修饰, 这时从句谓语动词要用第三人称单数,例如:
He seems not to have grasped what I meant, which greatly upsets me. 他似乎没抓住我的意思,这使我心烦。
Liquid water changes to vapor, which is called evaporation. 液态水变为蒸汽,这就叫做蒸发。

说明:关系代词that和关系副词why不能引导非限制性定语从句。

1)介词后面的关系词不能省略。
2)that前不能有介词。
3) 某些在从句中充当时间,地点或原因状语的"介词+关系词"结构可以同关系副词when 和where 互换。
This is the house in which I lived two years ago.
This is the house where I lived two years ago.
Do you remember the day on which you joined our club?
Do you remember the day when you joined our club?

由as, which 引导的非限定性定语从句,as和which可代整个主句,相当于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.

最终答案:略