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考点 20 主语从句&表语从句&同位语从句（重难考点精讲练）
考向二 主语从句
1.主语从句在复合句中充当主语，大多数主语从句都可以用it作形式主语而把主语从句置于句尾。
2.that引导主语从句时可用it作形式主语，that不可省；what引导的主语从句表示＂……的东西＂时，一般
不用it作形式主语；whatever，whoever，whichever一般也不用it作形式主语。
☞That she will succeed is certain.
☞It is certain that she will succeed.
常见的it替代that引导的主语从句的句式主要有以下几种：
(1)It＋系动词＋形容词(necessary，right，likely，unlikely，wrong，important，certain，clear，obvious，
strange，normal等)＋that从句
☞It is certain that most of the farmers have brought in more money by all means.
(2)It＋be＋名词(短语)(a pity，a shame，good news，a fact，an honour，a wonder，no wonder等)＋that从句
It’s no wonder that you’ve achieved so much success.
(3)It＋be＋过去分词(said，told，heard，reported，decided，suggested，advised，ordered，remembered，
thought，considered，wellknown，announced等)＋that从句
☞It is said that the professor has already succeeded in carrying out the experiment.
(4)It＋特殊动词(seem，appear，happen，matter)＋that从句
☞It happened to me that I had been away when he called.
注意：(1)在＂It is necessary/important/strange/natural...＋that从句＂结构中，从句谓语常用＂(should＋)
动词原形＂形式。
【拓展延伸】主语从句的引导词
引导词 作用 引导词 作用
that 无词义，在从句中不充当成分，但不能省略 how 多么，怎样，作方式状语或程度状语
who 谁，作主语、宾语 when 何时，作时间状语
whom 谁，作宾语 where 在哪儿，作地点状语
what 什么，可作主语、宾语、表语、定语 why 为什么，作原因状语
which 哪一个，哪些，作主语、宾语、定语 whether 是否
【特别注意】当作主语的句子太长时，为保持句子平衡，常用it作形式主语，而将真正的主语置后。if＂
是否＂，不可直接引导主语从句(用it作形式主语时可以) 。3. 主语从句的特殊用法
（1）主语从句与定语从句的转换
☞What is needed has been bought.
☞All that is needed has been bought.
所有需要的都被买了。
（2）几个特殊句型之间的转换
☞It is known to all that China has joined the WTO.
As is known to all, China has joined the WTO.
What is known to all is that China has joined the WTO.众所周知，中国已加入WTO。
4. 从句作主语时，句子谓语动词的单复数问题
(1)从句作主语时，谓语动词一般用单数。
That they are not going to the cinema is a big surprise to us.他们不去看电影，这使我们感到很惊讶。
(2)what引导的从向作主语，谓语动词一般用单数;若从句谓语或从句后的表语是复数形式,则谓语动词常用
复数。
What she said is wrong.她所说的是错误的。
What we need are books.我们所需要的是书籍。
1. ______ the path of a county is the right one is a matter to be decided by its people.
A. That B. What C. Whether D. Why
2. It soon became widely known ________ the attempt to save girl had failed.
A. that B. what C. who D. which
3. It suddenly occurred to him ________ he had left his keys in the office.
A. whether B. where
C. which D. that
考向四表语从句
引导表语从句的连接词主要有：
连接词：that，whether
连接代词：who，whom，whose，which，what，whoever whomever，whichever，whatever连接副词：when，where，how，why
1. 连接词引导
☞The reason for his absence is that he hasn’t been informed. 他缺席的原因就是他没接到通知。
☞The question remains whether they will be able to help us. 问题还是他们能否帮我们。
2. 连接代词和连接副词引导
☞The problem is who will take charge of this shop. 问题是谁将接管这家店铺。
☞That is when I realized the importance of journalism. 那时我才意识到新闻工作的重要性。
注意：
（1）as/as if/as though 引导的表语从句常跟在特定动词后面，如 seem，appear，look，taste，
sound，feel等。
☞It sounds as if someone is knocking at the door. 听上去好像有人在敲门。
☞At that time, it seemed as though I couldn’t think of the right word. 当时我似乎怎么也想不出一
个恰当的字眼来。
（2）当主句的主语是reason时，表语从句一般由that引导，这种用法常见于句型The reason why... is
that...
☞The reason why he came late was that he got up late. 他来得晚是因为起床晚了。
2表语从句的三个易混句式
句式 用法 例句
This/'That is why+结果 意为"这那就是.....to work there. That's why I want you to work there.
那就是的原因"，why 引导表语从
我想要你在那儿工作的原因。
句。
This/That/It is because 意为"这/那是因为.....，because引 It's just because he |doesn't know her.
+原因 导表语从句。 这
这仅仅是因为他不认识她 。
The reason why... is 意为"......的原因是……”， The reason why he didn't come was
that... why定语从句，修饰先行词reason, that it was raining heavily.他没有来的
that引导表语从句。 原因是 (当时)雨下得很大。
1. If you are addicted to your mobile phone, that’s ______ you should lay it down and be involved in meaningful
activities.A. when B. why C. where D. how
2. If you are addicted to your mobile phone, that’s ______ you should lay it down and be involved in meaningful
activities.
A. when B. why C. where D. ho w
3. Everyone on this planet is different, and that's______ makes it such a beautiful place.
A. When B. how C. what D. why
考向五 同位语从句
1. 同位语从句跟在名词后面，进一步解释、说明该名词的具体内容。同位语从句常跟在名词
idea, fact, news, hope, thought, suggestion等抽象名词之后；
2. 连接词that不能省略，无意义无成分；
3. 用whether而不用if引导同位语从句；
4. 连接代词who(m), which, what，whose在从句中作主语、宾语、表语或定语；
5. 连接副词where, when, why, how在从句作状语。
6.分割式同位语从句：同位语从句有时被别的词或短语把它和名词隔开：（谓语较短，同位语从句较长）。
☞The story goes that William Tell did kill the king with that sword.
7.若被同位语从句说明的名词是：advice, suggestion, proposal(建议), demand, request, requirement,
order(命令)等表示建议、命令、要求的词时，同位语从句的谓语用"(should)+do"。
8.区别由that 引导的定语从句和同位语从句：
①定语从句中的that是代词，可在从句中作主、宾、表；同位语从句中的that是连词，无成分无意义；
②定语从句——说明先行词的性质与特征，与先行词是修饰与被修饰的关系；
同位语从句——对名词即先行词加以补充说明，是名词全部内容的体现。
③在名词和从句之间加be, 使之构成一个新句子，如果合乎逻辑，句子通顺，则是同位语从句，定语从
句是不能用系表结构把先行词与从句连接起来的。
1. Evidence has been found through years of study _______ children’s early sleeping problems are likely to
continue when they grow up.
2. The only way to succeed at the highest level is to have total belief ______ you are better than anyone else on thesports field.
3. Evidence has been found through years of study______ children’s early sleeping problems are likely to continue
when they grow up.
1．The reason ________ you failed in the test yesterday, I suppose, was ________ you didn’t follow your teacher’s
advice.
A．which; because B．that; why C．why; that D．why; because
2．The most pleasant thing of the rainy season is ________ we can be entirely free from dust.
A．what B．which C．that D．how
3．Customers are becoming so practical nowadays that they only buy ________ they need.
A．that B．what C．when D．which
4．The old gentleman never fails to help ________ is in need of his help.
A．whom B．who C．whoever D．whomever
5．——Could you please tell me________?
——I’m not sure. Perhaps in a couple of days.
A．when he is coming back B．how many days he will stay there
C．how long will he be back D．how soon will he come back
6．The greatest mystery of all is ________ caused the Maya to abandon most of their great cities.
A．what B．where C．when D．which
7．It is universally acknowledged that money flows to ________ it is that controls the scarce thing.
A．whom B．whomever C．who D．whoever
8．About two thousand five hundred years ago the first houses appeared on the fat tops of the hills in ________ is
now northern New Mexico.
A．where B．which C．what D．that
9．________is the most important in life is that we should always be confident about the future.
A．Who B．Which C．That D．What
10．People may think that dinosaurs were big, green with hard skin covering their bodies. But in fact, it seems that
dinosaurs appeared very different from________ we think.
A．which B．that C．who D．what11．It is not a problem _____ we can win the battle; it’s just a matter of time.
A．whether B．why C．when D．where
12．He studied hard and later became a well-known writer, which was ______ his father had expected.
A．why B．how C．that D．what
13．The opinion learning is a lifelong process has been expressed by education experts throughout the
years.
A．which B．that
C．what D．how
14．Police have found ________ appears to be the lost ancient statue.
A．which B．where C．how D．what
15．________ was most important to her, she told me, was to keep healthy.
A．It B．This
C．What D．As
16．We choose this hotel because the price for a night here is down to $20, half of _______ it used to charge.
A．that B．which
C．what D．how
17．Every year, ________ makes the most beautiful kite will win a prize in the Kite Festival.
A．whatever B．whoever
C．whomever D．whichever
18．Students are always interested in finding out _______ they can go with a new teacher.
A．how far B．how long
C．how often D．how soon
19．_____________ comes will be welcome to the open-air concert.
A．Whatever B．Whoever
C．No matter what D．No matter who
20．It is not always easy for the public to see ________ use a new invention can be of to human life.
A．whose B．what C．which D．that
21．A computer can only do ___ you have instructed it to do .
A．how B．after C．what D．when
22．________ you said at the meeting describes a bright future for the company.
A．When B．HowC．What D．That
23．We should respect food and think about the people who don’t have we have here and treat food nicely.
A．that B．which C．what D．whether
24．—Is it true that Mike refused an offer from Yale University yesterday?
—Yeah, but I have no idea _____________ he did it; that’s one of his favorite universities.
A．when B．why
C．that D．how
25．The exhibition tells us _____we should do something to stop air pollution.
A．where B．why
C．what D．which
【2021】
1.（2021.6新高考1卷）
Going to Mount Huangshan reminds me of the popular Beatle's song "The Long and Winding Road". 1 is so
breathtaking about the experience is the out-of-this-world scenes.
2.（2021.3 天津卷）What puzzles Lily's friends is she always has so many crazy ideas.
A. whether B. why C. what D. when
3.（2021.1 浙江卷 语法填空）
BMI is an internationally recognized measurement tool 2 gives an indication of whether someone is a healthy
weight.
4.（2021.3 天津卷 单选）
At the Chinese art festival, there are different stands artists demonstrate their skills and teach the visitors.
A.where B.which C. that D. when
5.（2021.3 天津卷 单选）
William Hastie once suggested that history informs us of past mistakes we can learn without repeating
them.
A. from which B. in which C. with whom D. for whom【2020】
1. （2020江苏高考真题）It is not a problem __________ we can win the battle; it’s just a matter of time.
A. whether B. why C. when D. where
2. （2020天津高考真题）The student completed this experiment to make come true __________ Professor
Joseph had said.
A. that B. what C. when D. where
3. （2020浙江高考真题）Over thousands of years，they began to depend less on 57 could be hunted or
gathered from the wild, and more on animals they had raised and crops they had sown.
【2019】
1.【2019·江苏卷·单项填空】25.Scientists have obtained more evidence ___________ plastic is finding its way
into the human body.
A. what B. that C. which D. where
2.【2019·新课标I卷·语法填空】While they are rare north of 88°,there is evidence ___61___ they range all the
way across the Arctic, and as far south as James Bay in Canada.
【2018】
1.【2018·北京】11. Without his support, we wouldn’t be _________ we are now.
A. how B. when C. where D. why
2.【2018·北京】15. This is _________ my father has taught me—to always face difficulties and hope for the best.
A. how B. which C. that D. what
3.【2018·天津】9. The gold medal will be awarded ___________to wins the first place in the bicycle race.
A. whomever B. wherever C. whoever D. whatever
4.【2018·江苏】21. By boat is the only way to get here, which is _______ we arrived.
A. where B. when C. why D. how
【2017】
1.【2017·北京】23. Every year, ______ makes the most beautiful kite will win a prize in the Kite Festival.
A. whatever B. whoever C. whomever D. whichever
2.【2017·北京】26. Jane moved aimlessly down the tree-lined street, not knowing ______she was heading.
A. why B. where C. how D. when
3.【2017·江苏】26. We choose this hotel because the price for a night here is down to $20, half of _______ it used
to charge.
A. that B. which C. what D. how4.【2017·天津】4. She asked me _______ I had returned the books to the library, and I admitted that I hadn’t.
A. when B. where C. whether D. what
4.【2018·新课标II卷·短文改错】The games my parents taught me where I was a child turned out to be very
useful later in my life.
