高考英语二轮语法专题复习-专题 9 定语和定语从句导学案（含答案）-2026届高三英语上学期一轮复习专项

高考英语语法专题复习
专题9 定语和定语从句
目 录
考点1 定语从句的常见引导词 4
考点2 关系代词引导的定语从句 6
1. 关系代词who/whom 6
2. 关系代词which 7
3. 关系代词that 7
4. 关系代词whose 8
5. as引导的定语从句 8
考点3 关系副词引导的定语从句 10
1. 关系副词when/where 10
2. 关系副词why 11
考点4 关系代词which和that的区别 12
1. 在限制性定语从句中只能用that，不能用which作关系代词的情况 12
2. 只用which，不能用that作关系代词的情况 13
考点5 “介词+关系代词”引导的定语从句 14
考点6 定语从句的转换 16
七、专项练习 18
八、答案解析 25
定语和定语从句
定语：由单词、短语或从句对名（代）词修饰和限制，该名（代）词称为中心词。定语一般前置，短语和从句作定语要后置，翻译成“……的”。除了形容词，名词、数词、非谓语动词（短语）、介词短语也可以作定语。
a beautiful girl（形容词作前置定语）一个美丽的女孩
a girl in white（介词短语作后置定语）一个穿白色衣服的女孩
a girl who is singing（定语从句，a girl为先行词）一个正唱歌的女孩
定语从句：用来说明主句中某一名词或代词（有时也可说明整个主句或主句中的一部分）而起定语作用的句子称为定语从句。定语从句也称为形容词性从句。
定语从句分为限制性定语从句和非限制性定语从句两种。限制性定语从句是先行词不可缺少的部分，去掉从句后，主句意思往往不明确。
A man who doesn’t learn from others can’t achieve much. 一个不向别人学习的人是不会有多少成就的。（A man被限定后，指一类特定的人，此时定语从句是不能去掉的，否则主句就失去意义，含义不清，甚至让人感到莫名其妙。）
非限制性定语从句则不然，它只对所修饰的词做进一步的说明，去掉之后并不影响主句的含义。在形式上，非限制性定语从句与主句之间通常用逗号隔开。
Finally we visited the Three Gorges Dam, which is the greatest key water control project in the world at present. 最后，我们参观了长江三峡大坝，它是目前世界上最大的水利枢纽工程。（该句若去掉从句，主句部分的含义仍然完整。）
另外，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。
The traffic of this city is quite bad, which is known to everyone.
这座城市的交通很糟糕，这一点大家都知道。
考点1 定语从句的常见引导词
定语从句中的引导词称为关系词，分为关系代词和关系副词。
引导词 功能和作用 替代 (人、毕、物) 用于 限制/非限制 在定语从句中所作成分
关系代词 that 人或物 限制 主、宾、表
which 事物 限制或非限制性 主、宾、表
who 人 限制或非限制性 主、宾、表
关系代词 whom 人 限制或非限制性 宾、表
whose 人或物 限制或非限制性 定语
as 人或物 限制或非限制性 主、宾、表
关系副词 when 时间 限制或非限制性 时间状语
where 地点原因 限制或非限制性 地点状语
why 人 限制 原因状语
注意：① 定语从句中的谓语动词要与先行词的人称和数保持一致。
Tom is one of the boys who are from the USA. 汤姆是众多来自美国的男孩中的一个。
Tom is the only boy that is from the USA. 汤姆是唯一从美国来的男孩。
② that只引导限制性定语从句。
③ what不能引导定语从句。
④ 在限制性定语从句中，当关系代词who, whom, which和that用作动词宾语或介词宾语（介词位于句末）时，可以省略。关系词在非限制性定语从句中不能省略。
Is there anything（that）you wanted 你想要什么东西吗？
Who is the man, whom you were talking to 刚才和你讲话的人是谁？
考点2 关系代词引导的定语从句
关系代词that, which, who, whom, whose, as引导的定语从句
关系代词主要有that, who, whom, whose, which, as等，其中who和whom只用于指人，which和as只用于指事物，whose和that既可用于指人也可用于指物，它们在定语从句中可用作主语、宾语、表语或定语。
1. 关系代词who/whom
关系代词who/whom指人，在定语从句中分别作主语和宾语。
The man who lives in that house is my uncle.
住在那座房子里的人是我叔叔。（who指人，在从句中作主语）
The girl（whom）the teacher often praises is our monitor.
老师经常表扬的那个女孩是我们的班长。
Peter, whom you met in London, is now back in Paris.
彼得现在回巴黎了，你在伦敦见过他。
注意：关系代词whom 在口语或非正式文体中常可用who 来代替。
The man（whom/who）you met just now is my old friend.
你刚才见到的那位男士是我的老朋友。
2. 关系代词which
关系代词which 指物，在定语从句中作主语或宾语。
The book which cost me a lot of money is very interesting.
我花很多钱买来的那本书很有趣。
My sister likes the gift（which）I gave her yesterday. 妹妹喜欢我昨天送她的礼物。
European football is played in 80 countries, which makes it one of the most popular sports in the world. 有80个国家在踢欧式足球，这使它成为全世界最流行的体育运动之一。
3. 关系代词that
关系代词that 指人时，相当于who 或whom；指物时，相当于which，在定语从句中作主语或宾语。
The bag that（=which）lies on the ground is hers. 地上的那个包是她的。
The old man that（=whom/who）I visited yesterday is my teacher.我昨天拜访的那位老人是我的老师。
4. 关系代词whose
关系代词whose通常指人，也可指物，在定语从句中作定语。
I visited a scientist whose name is known all over the country.
我拜访了一位全国知名的科学家。
I once lived in the house whose roof has fallen in.
我曾经住在那幢屋顶已经倒塌了的房子里。
注意:指人或物时，常用of whom/of which结构来代替：
Do you know the doctor, whose son is a doctor too =Do you know the doctor, the son of whom/of whom the son is a doctor too
你认识那位医生吗？他的儿子也是一名医生。
There is a church, whose door faces south.=There is a church, the door of which/of which the door faces south.
有一座教堂，窗户朝南。
5. as引导的定语从句
（1）as引导的限制性定语从句：
as引导限制性定语从句时，它通常要与such, the same, as搭配，即构成such... as..., the same... as..., as... as... 这样的固定搭配，同时as在从句中充当一定的句子成分。
He is not such a fool as he looks. 他并不像看上去那样愚蠢。
He rides as expensive a bike as he can afford. 他骑一辆他买得起的最贵的自行车。
I have bought the same watch as you have. 我买了一块和你一样的手表。
（我的手表和你的手表很像，但不是同一块，故由as引导定语从句。）
This is the same watch that I lost. 这就是我丢的那块手表。
（这块手表和我丢的手表是同一块，故由that引导定语从句。）
（2）as引导的非限制性定语从句
as引导非限制性定语从句时，代替整个主句，对其进行说明，通常用于as we all know, as it is known, as is known to all, as it is, as is said above, as always mentioned above, as is usual, as is often the case, as is reported in the newspaper等句式中。as在非限制性定语从句中作主语、表语或宾语，且引出的从句位置比较灵活，可位于句首或句末，也可置于主句中间。通常均由逗号将其与主句隔开。as有“正如……，就像……”之意。
As is known to the United States, Mark Twain is a great writer.
美国人都知道，马克·吐温是一位伟大的作家。（as在从句中作主语）
He is absorbed in work, as he often was.
他正在全神贯注地工作，他过去经常这样。（as在从句中作表语）
As we all know, the earth is round.
众所周知，地球是圆的。（as在从句中作宾语）
考点3 关系副词引导的定语从句
关系副词主要有when, where和why，其中when表示时间，where表示地点，why表示原因，它们在定语从句中均用作状语。
1. 关系副词when/where
关系副词when/where 既可引导限制性定语从句，又可引导非限制性定语从句。先行词是时间或地点名词，在从句中充当时间状语或地点状语，相当于“介词+which”。
October 1, 1949 was the day when（=on which）the People’s Republic of China was founded. 1949年10月1日是中华人民共和国成立的日子。（限制性定语从句）
This is the school where（=in which）I studied a few years ago.
这就是我几年前读书的学校。
I will never forget the day, when（=on which）I joined the Party.
我入党的那一天，我永远不会忘记。（非限制性定语从句）
Let’s go to the concert, where（=in which）you will find much fun.我们去听音乐演唱会吧，在那里你会找到很大的乐趣。
where有时还可用于抽象名词后引导定语从句。常见此类抽象名词有point, degree, stage, position, case, condition等。
We have reached a point where a change is needed. 我们到了必须要改变的地步。
He got into a situation where it is hard to decide what is right and wrong.他陷入一种难以分辨是非的局面。
I don’t want a job where I’m chained to a desk all day.我不想找一份整天坐办公桌前的工作。
2. 关系副词why
关系副词why只能引导限制性定语从句，先行词只有reason一词，在从句中充当原因状语，相当于for+which。
Do you know the reason why（=for which）he is not here now
你知道他还没有来这儿的原因吗？
注意:用关系代词还是关系副词引导定语从句主要看关系词在定语从句中的作用（即所担当的成分）。试比较：
I know a place where we can have a picnic. 我知道一个我们可以野炊的地方。
I know a place which/that is famous for its beautiful natural scenery.我知道一个以自然景色优美而闻名的地方。
I will never forget the days when we spent our holidays together.我永远忘不了我们一起度假的日子。
I will never forget the days that/which we spent together.我永远忘不了我们一起度过的日子。
This is the reason why he was dismissed. 这就是他被解雇的原因。
This is the reason that/which he explained to me for his not attending the meeting.这就是他向我解释的他没有参加会议的原因。
考点4 关系代词which和that的区别
在先行词是事物的限制性定语从句中，that和which一般可互换。关系代词that只引导限制性定语从句，不能引导非限制性定语从句。
1. 在限制性定语从句中只能用that，不能用which作关系代词的情况
（1）当先行词是everything, anything, nothing, all, none, few, little,some等不定代词时，或当先行词被every, any, all, some, no, little, few,much等词修饰时。
All that can be done has been done.
所有能做的都做了。
（2）先行词被序数词、形容词最高级、the only, the very, the last等词修饰时。
The first place that they visited in London was the Big Ben.
在伦敦他们参观的第一个地方是大本钟。
It’s the most important task that should be finished soon.
这是需要马上完成的最重要的任务。
（3）先行词既有人又有物时。
They talked about the persons and things that they remembered at school.
他们谈论了他们所能记起的在校时的人和事。
（4）当先行词前面有who, which等疑问代词时，为避免混淆，不用which而用that。
Who is the man that is standing by the gate 站在门口的那个人是谁
2. 只用which，不能用that作关系代词的情况
（1）在非限制性定语从句中只能使用关系代词which，不能使用关系代词that。
He made another wonderful theory discovery, which I think is of great importance to science. 他做出了另外一项精彩的发现，我认为这一发现具有重要的科学意义。
（2）在“介词+关系代词”引导的定语从句中，只能使用关系词which，不能使用that。
The house in which we live is very large. 我们住的房子非常大。
注意:如果介词不放在关系代词之前，which就可换为that。
This is the question about which we’ve had so much discussion.=This is the question which/that we’ve had so much discussion about. 这就是我们已经多次讨论过的问题。
考点5 “介词+关系代词”引导的定语从句
关系代词在定语从句中作介词宾语时，从句常常由“介词+关系代词”引出。
The school in which he once studied is very famous. =The school（which/that）he once studied in is very famous. 他曾经就读过的学校很出名。
注意:
（1）定语从句中某些含有介词的短语动词一般介词仍放在短语动词的后面，此类动词短语有：look for, look after, take care of等。
This is the watch（which/that）I am looking for. 这是我正在寻找的手表。
This is the watch for which I am looking.（×）
（2）关系代词在定语从句中作介词的宾语且介词前置时，只能用which或whom, 不可用who, that。
The man with whom you talked just now is my neighbour.
你刚才跟他谈话的那个人是我的邻居。
The plane in which we flew to Canada was really comfortable.
我们去加拿大所乘坐的飞机很舒服。
（3）“介词+关系代词”前还可有some, any, none, all, both,neither, many, most, each, few等代词或者数词。
There are forty students in our class in all, most of whom are from big cities.
我们班总共有40个学生，大多数来自大城市。
Up to now, he has written ten novels, three of which are about country life.
迄今为止，他写了10部小说，其中3部是关于农村生活的。
（4）以the way为先行词的限制性定语从句通常由in which或that引导，而且通常可以省略。
The way（that/in which）he answered the questions was surprising.
他回答这些问题的方式令人惊讶。
考点6 定语从句的转换
定语从句可以转换为形容词（短语）、非谓语动词（短语）、介词短语等形式。
（1）非限制性定语从句转化为两个简单句、并列句、独立主格或同位语形式。
I found many flowers in the garden, most of which were red.→
① I found many flowers in the garden; most of them were red.（两个简单句）
② I found many flowers in the garden. Most of them were red.（两个简单句）
③ I found many flowers in the garden, and most of them were red.（并列句）
④ I found many flowers in the garden and most of them were red.（并列句）
⑤ I found many flowers in the garden, most of them red.（独立主格）
我在花园里看到了很多花儿，大部分都是红色的。
We finally reached London, which was the end of our journey.→We finally reached London, the end of our journey.（同位语）
我们抵达了伦敦——我们行程的终点。
（2）限制性定语从句可以转化成含有形容词、非谓语动词或介词的短语。
1）在定语从句中，如果谓语动词是主动语态，就用现在分词短语替换；如果是被动语态，可用过去分词替换；如果是单个动词要放在中心词之前，动词短语要后置。
① The girl who is crying is my sister.→The crying girl is my sister. 正在哭泣的女孩是我的妹妹。
② The girl who is crying behind the tree is my sister.→The girl crying behind the tree is my sister. 在树后哭泣的女孩是我的妹妹。
③ This is a story which was written by Charles Dickens.→This is a story written by Charles Dickens. 这是由查尔斯·狄更斯创作的一个故事。
④ The man who owns that car will be fined for illegal parking.→The man owning that car will be fined for illegal parking.那辆车的车主将会因为违章停车而被罚款。
2）在定语从句中，如果含有情态动词或先行词前有序数词first,last, next等，可以将其转化为含有不定式作定语的简单句。
① You need someone who can look after you.→You need someone to look after you. 你需要有人来照顾。
② Mary was the first student who arrived at the square.→Mary was the first student to arrive at the square. 玛丽是最先到达广场的学生。
3）在定语从句中，如果谓语动词含有be的形式，表语是介词短语、形容词（短语），在不影响理解的前提下，可以转化成上述短语作定语的简单句。
① The girl who is behind the tree is my sister.→The girl behind the tree is my sister. 树后面的那个女孩是我的妹妹。
② Soldiers must be people who are not afraid of death.→Soldiers must be people not afraid of death. 军人必须是不畏牺牲的人。
七、专项练习
I. 单句改错。（仅限1处）
1. The citizens welcomed the new mayor, most of who are workers.
2. Who is the soldier gave us a speech last month
3. All what she could do was to go to church.
4. I, who is in Australia, feel proud of being a Chinese.
5. The girl failed in the exam, that made us disappointed.
6. We got on the school bus and which took us straight to the People’s Park.
7. He built a transparent wall through that he could observe what was going on.
8. This is the only English-Chinese dictionary which I could find in the shop.
9. I don’t like the way which he spoke to his teacher.
10. Don’t leave the medicine bottle which the little boy can reach it.
II. 在空白处填写1个适当的单词或括号内单词的正确形式。
11. I live next door to a couple ______ children often make a lot of noise.
12. We will put off the picnic in the park until next week, ______ the weather may be better.
13. Scientists have advanced many theories about why human beings cry tears, none of ______ has been proved.
14. ① He is the only one of the teachers who ______（know）French in our school.
② This is one of the rooms that ______（be）free now．
15. We’d better fix a date ______ which we will practice speaking English next week.
16. Earthquake is a sudden shaking of the earth’s surface ______ may cause great damage.
17. ① ______ is well known to all, China has the largest population in the world.
② He didn’t win the championship, ______ I hadn’t expected.
18. That Peter will marry Alice, ______ has not been announced yet, has spread around.
19. ① The novel which ______（give）by the professor yesterday mainly discusses the development of Chinese economy.
② The novel ______（give）by the professor yesterday mainly discusses the development of Chinese economy.
20. ① On Sundays there were a lot of children playing in the park,______ parents seated together joking.
② On Sundays there were a lot of children playing in the park, _______parents were seated together joking.
III. 单项选择。
21. The 11th of September is a special date, ______, I think, that will be remembered by the Americans forever.
A. what
B. it
C. which
D. one
22. The factory produced many famous cars, none of ______ shipped to foreign countries.
A. them
B. which
C. it
D. what
23. It wasn’t such a good present ______ my cousin had promised me.
A. that
B. as
C. which
D. what
24. ① ______ leaves the room last ought to turn off the lights.
② ______ who leaves the room last ought to turn off the lights.
③ ______ who leave the room last ought to turn off the lights.
A. Anyone
B. Who
C. Those
D. Whoever
25. This is the only way ______ you can find. By the way, I don’t like the way ______ he spoke to his mother.
A. that; 不填
B. in which; 不填
C. which; which
D. which; that
26. ① Is this museum ______ they visited last month
② The teacher tells us that ______ cleans the blackboard is to be praised.
A. that
B. the one
C. which
D. the one who
27. ① It was eleven o’clock ______ they went out of the cinema.
② It was at eleven o’clock ______ they went out of the cinema.
A. which
B. that
C. when
D. on which
28. —Where did you get to know her
—It was on the farm ______ we worked.
A. that
B. there
C. which
D. where
29. Edward is the boy ______ I think scored the winning points for the basketball team.
A. whom
B. which
C. what
D. who
30. I shall never forget those years ______ I lived in the country with farmers, ______ has a great effect on my life.
A. that; which
B. when; which
C. which; that
D. when; who
IV. 阅读下列短文，在空白处填写1个适当的单词或括号内单词的正确形式。
Scientists 31 study primates（灵长类）say that we are moving towards a time 32 species like gorillas（大猩猩）will no longer be found in the wild. Jo Setchell is a primatologist at Durham University in Britain. She studies primates, the group of mammals 33 includes gorillas, chimps and monkeys. And, of course, humans.
In all, there are an estimated 600 different species of primates. They include the little creature called the mouse lemur（鼠狐猴）, 34 body is only about six centimeters long. Then, there is the largest of the species, the gorilla, 35 weighs up to 250 kilograms.
Primates face one common threat: loss of habitat, the places in nature 36 they live. Primatologists like Setchell say human activity is to blame. More than half of all primate species are grouped in four countries: Brazil, Indonesia, Madagascar and the Democratic Republic of Congo. Paul Garber says each of these countries is working to help protect the primates in their areas, 37 there is neither the funds, community support nor in-country expertise to address their conservation problems.
Madagascar is a good example of these problems, he says. It is home to over 100 primate species, almost all of 38 live nowhere else. And 94 percent of them are endangered. Ninety percent of the original forests of Madagascar have been cut down, Garber says.Neither Garber nor Setchell have any easy answers about how to stop this road to extinction.
“We knew that primates were in trouble, but I think even for those of us 39 work in primate conservation, it was still shocking to discover quite what the scale of the problem is.”
40 the scientists know, the clearest way is to slow human activity in primates’ habitats. The decrease is reversible if humans make primate and habitat conservation a top concern.
八、答案解析
I.
1. who改为whom 考查关系代词。关系代词who不可以放在介词后面。
2. 在gave前加that或把gave改为giving 考查定语从句或非谓语动词。注意关系代词作主语不能省略，因句中已有who，为避免歧义，本句不能使用who。若改为giving，则为现在分词短语作后置定语。
3. 删除what或者把what改为that 考查定语从句。all为不定代词，充当先行词时需用that引导定语从句，此处that在定语从句中充当do的宾语，可以省略。what不是关系词，不可以引导定语从句。当然，本句还可以把all删除，将what的首字母大写（此时what引导主语从句），但是这涉及两处改动。
4. is改为am 考查定语从句中的主谓一致。应根据先行词I确定谓语动词的形式。
5. that改为which或as 考查定语从句。which和as引导定语从句时，可以代替整个句子。注意：位于句首时只能用as，即As made us disappointed, the girl failed in the exam.
6. which改为it或者把and删除，或者把and改为逗号考查句子结构。若改which，整句为and连接的并列句，若改and，which引导的是定语从句。
7. that改为which 考查“介词+关系代词”引导的定语从句。定语从句中如果介词提前，介词后只能跟which/whom。
8. which改为that 考查关系代词。当先行词被only修饰时，定语从句只能用that引导。
9. which改为that，或在which前加in，或去掉which 考查关系代词。先行词为way（方式，方法）时，定语从句可以用that/in which引导，也可以省略。
10. which改为where 考查定语从句和状语从句的区别。句意：别把药瓶放在孩子可以够到的地方。这是地点状语从句（由where引导），而不是定语从句，因为没有先行词。
II.
11. whose 考查定语从句的关系词。句意：我的隔壁住着一对夫妇，他们的孩子经常很吵。 a couple是先行词，这对夫妻的孩子很吵，children和couple是所属关系，故用whose作定语，相当于the children of whom。
12. when 考查定语从句。句意：我们将把公园野餐推迟到下个星期，那时天气可能会更好。定语从句的先行词是next week，定语从句中不缺少主宾表，缺少时间状语，故为when。
13. which 考查非限制性定语从句。句意：关于人类为什么哭的时候会流泪，科学家已经提出了很多理论，没有一个被证明了。先行词是theories，指物，定语从句中用which引导。
14. ① knows 考查定语从句中的主谓一致。句意：他是我们学校中唯一懂法语的教师。因为one前有the only之类限定词，定语从句在意义上修饰的是the only one，是单数，而不是复数名词the teachers。② are考查定语从句中的主谓一致。句意：这是目前空着的房间之一。因为one前没有the only之类的限定词，定语从句在意义上修饰的是名词复数the rooms，而不是单数one。
15. on 考查“介词+关系代词”引导的定语从句。当先行词表示时间，定语从句中缺少时间状语时，通常用关系副词when引导，此时也可选用表示时间的“介词+which”来代替关系副词when。
16. which/that 考查定语从句。句意：地震是地球表面突然的震动，地震会造成重大的损失。定语从句中缺乏主语，故为which/that。
17. ① As 考查as引导的非限制性定语从句。句意：众所周知，中国拥有世界上最多的人口。
② which 考查which引导的非限制性定语从句。句意：他没获得冠军，这一点是我没预料到的。表示“正如”的含义时，通常用as引导非限制性定语从句，也可用which引导；但置于句首时，只能用as引导。当非限制性定语从句是否定含义时，只能用which，而不用as引导。
18. which 考查which引导的定语从句。句意：彼得要娶爱丽斯这件事还没宣布却已传得沸沸扬扬。引导非限制性定语从句的which可以指代前面的先行词，也可以指前面整个句子的含义。句子中的which指“彼得要娶爱丽斯”这整个句子的意思。
19. ① was given ② given 前者考查定语从句中的时态和语态；后者考查过去分词短语作后置定语。
20. ① their ② whose 考查独立主格及非限制性定语从句。前者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，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。后者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。
III.
21. D 考查代词及定语从句。one作date的同位语，后面跟that引导的定语从句，I think是插入语。
22. A 考查独立主格。句意：这个工厂生产很多名牌汽车，其中没有一辆运往国外。ship在这里是一个及物动词，意思是“运送……到”；shipped是过去分词，此处是“代词+过去分词短语”构成的独立主格结构。如果在shipped前面加was，则应该选B项，构成非限制性定语从句。
23. B 考查定语从句。句意：这不是我表兄曾经答应给我买的那样好的礼物。先行词前面有such修饰，因此选择as，引导定语从句。
24. ① D ② A ③ C 句意：最后离开这个房间的人应该关上灯。 ①考查主语从句，whoever 引导主语从句；② 考查定语从句，anyone为先行词，后面who引导定语从句，anyone who... 相当于whoever；③ 考查定语从句，those既为整个句子的主语，也是定语从句的先行词，后面为who引导的定语从句。
25. A 考查定语从句。第一空先行词为way，前面有the only 修饰，故关系代词用that，由于在定语从句中作宾语，也可以省略。第二空中的way意为“方式”，当way表示“方式，方法”且在句中作先行词时，引导定语从句可用that，也可用in which，也可以省略。
26. ① B ② D考查定语从句。句①陈述语序为This museum is _____they visited last month. 句子中缺乏表语，因此选the one作表语，同时为先行词，在后面定语从句they visited last month 作宾语，故关系代词可以省略；句②中that后面为宾语从句，宾语从句中缺乏主语，主干应该为the one is to be praised，而the one作主语，同时为先行词，在后面定语从句cleans the blackboard中作主语，故指代它的关系代词who不可以省略。
27. ① C ② B 前者考查时间状语从句，句中when引导时间状语从句；后者考查强调句型。
28. D 考查定语从句和省略。这道题很多考生误选A，因为强调句型的经典结构“it is+被强调的部分+that+从句”。此题中，“that+从句”已被省略，正确答案为where。句中where we worked是定语从句，修饰the farm。该强调句补充完整应为：It was on the farm where we worked that I got to know her.
29. D 考查定语从句。本句中，who引导一个嵌入式定语从句：who scored the winning points for the basketball team，先行词为the boy，而I think相当于插入语，由于关系词指人，又在从句中起主语作用，故应选用who。
30. B 考查定语从句。第一个定语从句缺时间状语，因此第一空应该使用关系副词when；第二个定语从句缺主语，关系代词指代前面整句话，因此用which引导非限制性定语从句。
IV.
语篇解读：本文主要介绍了大猩猩之类的野生灵长类动物濒临灭绝的状况。
31. who/that 考查限制性定语从句。先行词为scientists，定语从句缺少主语，故填who或that。
32. when 考查限制性定语从句。先行词为a time，定语从句中缺少时间状语。
33. that/which 考查限制性定语从句。先行词为the group of mammals，定语从句缺少主语，故填that或which。
34. whose 考查限制性定语从句。先行词为mouse lemur，定语从句中缺少定语，故填whose。
35. which考查非限制性定语从句。先行词为the gorilla，定语从句中缺少主语，故填which。
36. where 考查限制性定语从句。先行词为the places，定语从句中缺少地点状语，故填where，相当于in which。
37. where 考查非限制性定语从句。先行词为their areas，定语从句中缺少地点状语，故填where，相当于in which。
38. which考查非限制性定语从句。先行词为primate species，定语从句中缺少主语，故填which。
39. who考查限制性定语从句。先行词为those of us，定语从句中缺少主语，故填who。
40. As 考查非限制性定语从句。as 引导非限制性定语从句，可放在主句之前或者主句之后，which 引导的非限制性定语从句只能放在主句之后。另外，as 有“正如……，正像……”的意思。