引导宾语从句时，that通常可以省略，但引导主语、表语和同位语从句时，that不能省。例如：
China’s success in manned-spacecraft travel shows ____ our country has become one of the greatest powers in space research. A. what B. which C. 不填 D. it that
解析：该句中的从句作shows的宾语，是宾语从句，又因为从句中不缺主、宾语，所以只能用that引导；又因引导宾语从句时that可以省略，所以答案是C。
九、同位语从句引导词where, when的用法特点
说明先行词内容的同位语从句的引导词where, when与被说明的名词在概念上不一致。但引导定语从句的引导词却必须保持一致。是比较： Then arose the question ____ we were to get so much money.
This the house ____ the great man Mao Zedong was born 110 years ago. A. where B. that C. about which D. in which
解析：答案分别是(1) A (2) A/D。先行词与where, when概念一致时，是定语从句，（2）中的house与where同表地点，且这个关系副词where或when可以用“介词+which”的形式代替，所以答案A 和D都可以引导。（1）题中的question与where不表同一概念，可见是同位语从句，所以where不能改用“介词+which”的形式。
定语从句
1.定语从句：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。
2.关系词：引导定语从句的关联词称为关系词，关系词有关系代词和关系副词。关系代词有that, which, who, whom, whose, as等；关系副词有where, when, why等。关系词常有3个作用：1，引导定语从句。2，代替先行词。3，在定语从句中担当一个成分。 注：关系代词有主语.宾语之分。一般whom作为宾语。
4.定语：定语用来限定、修饰名词或代词的，是对名词或代词起修饰、限定作用的词、短语或句子，汉语中常用‘??的’表示。主要由形容词担任。此外，名词，代词，数词，分词，副词，不定式以及介词短语也可以来担任，也可以由一个句子来担任．单词作定语时通常放在它所修饰的词之前，作前置定语。短语和从句作定语时则放在所修饰的词之后，作后置定语。
先行词：被定语从句修饰的名词、代词称为先行词。 （十一）定语从句的难点分析
（一）限制性定语从句只能用that的几种情况
1．当先行词是anything, everything, nothing (something 除外), few, all, none, little, some等代词时，或者是由every, any, all, some, no, little, few, much，each等修饰时
(1) Have you taken down everything (that) Mr. Li has said?
(2) There seems to be nothing (that) seems impossible for him in the world. (3) All that can be done has been done.
(4) There is little (that) I can do for you.
注意1：部分时候that可以省略，如部分例句将that用括号括住。 注意2：当先行词指人时，偶尔也可以用who
(4) Any man that/.who has a sense of duty won’t do such a thing. 2. 当先行词被序数词修饰
(1) The first place that they visited in London was the Big Ben. 3. 当先行词被形容词最高级修饰时
(1) This is the best film that I have seen.
4. 当形容词被the very, the only，the same,the last 修饰时 (1) This is the very good dictionary that I want to buy,
(2) After the fire in his house, the old car is the only thing that he owned. 当先行词指人时，偶尔也可以用who
(3) Wang Hua is the only person in our school who will attend the meeting？ 5. 当先行词前面有who, which等疑问代词时 (1) Who is the man that is standing there? (2) Which is the T-shirt that fits me most? 6. 当先行词既有人，也有动物或者物体时
(1) Can you remember the scientist and his theory that we have learned? 7.当关系代词在定语从句中做表语或先行词本身就作主语的表语
(1)The village is no longer the one that it used to be 10 years ago. (2)This is a good book that will help you a lot.
（二）关系代词as和which引导的定语从句as和which引导非限制性定语从句，有相同之处也有不同之处。具体情况是： 1．As和which都可以在定语从句中做主语或者宾语，代表前面整个句子。 (1) He married her, as/which was natural. (2) He was honest, as/which we can see.
2. as 引导非限制性定语从句，可放在主句之前，或者主句之后，甚至可以切割一个主句；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
(1) As is known to all, China is a developing country. (2) He is from the south, as we can see from his accent. (3) John, as you know, is a famous writer.
(4) He has been to Paris more than several times, which I don’t believe. 注意：当主句和从句存在逻辑上的因果关系时，常用which
(5) Tom was always late for school, which made his teacher angry. 3. 当先行词受such, the same修饰时，常用as
(1) I have never heard such a story as he tells. (2) He is not such a fool as he looks.
(3) This is the same book as I lost last week.
注意：当先行词由the same修饰时，偶尔也用that引导定语从句，但是和由as所引导的定语从句意思不同 (4) She wore the same dress that she wore at Mary’s wedding. 她穿着她在MARY婚礼上穿过的一条裙子。
(5) She wore the same dress as her young sister wore. 她穿着和她妹妹所穿的一样的裙子。 注意：定语从句such?as ?与结果状语从句such? that
?的区别：as在所引导的定语从句中作主语，宾语；that在结果状语从句中不做成分 (6)He has such a good laptop as I want to buy.
(7)He has such a good laptop that I want to by one.
(三）以the way为先行词的定语从句通常由in which, that引导，而且通常可以省略。 (1) The way in which/ that/./ he answered the question was surprising. (四) but有时也可以做关系词引导定语从句
(1) There are very few but understand his idea. ( but= who don’t )
(五) 区分定语从句和同位语从句
1．定语从句修饰先行词，它和先行词是修饰关系； 同位语从句说明先行词的具体内容，是补充说明的关系
(1) The plane that has just taken off is for London. 定语从句 (2) The fact that he has been dead is clear. 同位语从句
2．定语从句由关系代词或者关系副词引导，关系词在句中充当成分，有时可以省略； 同位语从句主要由that引导，在句中一般不做成分；
句子也可以由when, where, how, why, whether, what等词引导，充当成分 (1) The news he told me is true.
(2) The news that he has just died is true.
(3) The problem that we are facing now is how we can collect so much money. 定语 (4) The problem how we can collect so much money is difficult to solve.
3. 同位语从句和先行词一般可以用be动词发展成一个完整的句子，而定语从句不可以 (1) The idea that we could ask the teacher for advice is wonderful. 同位语 (2) The idea was that we could ask the teacher for advice.
(3) The fact that the earth moves around the earth is known to all. (4) The fact is that the earth moves around the earth. 18. 定语从句
定语从句（Attributive Clauses）在句中做定语，修饰一个名词或代词，被修饰的名词,词组或代词即先行词。定语从句通常出现在先行词之后，由关系词（关系代词或关系副词）引出。
关系代词有：who, whom, whose, that, which等。 关系副词有： when, where, why等。 18.1 关系代词引导的定语从句
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在句中作宾语） 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） ［定语从句］介词+关系词
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。例如： This is the house in which I lived two years ago. 这是我两年前住过的房子。 This is the house where I lived two years ago.
Do you remember the day on which you joined our club？ 还记得你加入我们俱乐部的那一天吗？ Do you remember the day when you joined our club？
宾语从句
宾语从句 在句子中起宾语作用的从句叫做宾语从句.宾语从句分为三类:动词的宾语从句,介词的宾语从句和形容词的宾语从句. 时态：
1.主句用一般现在时，从句可用任意时态。 2.主句用过去时，从句用过去某个时态。
3.主句用过去时，从句是真理时，只用一般现在时。 宾语从句（版本四） 一、定义和宾从例句分析
宾语从句就是一个句子作动词或介词的宾语。 A 作动词的宾语: I heard the news.
主语 谓语动词 名词作宾语
I heard that he would come here later on. 主语 谓语动词 一个句子作宾语---宾语从句 B 作介词的宾语:
He said nothing about the plan.
主语 谓语动词 代词作动词的宾语 介词 名词作介词的宾语
He said nothing about who broke the window last night. 主语 谓语动词 代词作动词的宾语 介词 一个句子作介词的宾语
二、带有宾语从句的复合句的构成
带有宾语从句的复合句就是用连接词把一个主句和一个宾语从句连接在一起。连接词有：that(可省略)，what, who, when, where, why, which, if, whether, how. 1 He suggested (that) we should clean the corridor every day. 宾语
2 He told me (that) he would leave Dalian airport at 8pm. 间接宾语 直接宾语
3 He told me where he was going to travel that summer. 间接宾语 直接宾语
4 He wanted to know what the manager had said at the meeting. who hadn’t passed the exam.
when she would leave this building. why she cried last night. where she was going to study.
which student was his partner in the short play.
if (whether) Tom could play basketball with him that morning. how she managed to solve the problem.
why water flows from a high position to a lower position.
在例子4中，当主句是过去时态时（一般过去时，过去进行时，过去将来时，过去完成时），从句根据不同情况必须使用过去时态的一种，（大自然的现象和真理除外）。
5 He is wanting to know what I can cook for dinner. who broke the window yesterday. when I can have a holiday.
why I failed the exam yesterday.
where I should have dinner with my friend tonight. which book is the best one.
if (whether) I have passed the exam.
how my cat escaped from the room last night.
在例子5中，当主语是现在时态时（一般现在时，现在进行时，一般将来时，现在完成时），从句可根据不同情况使用各种时态。 三、注意
A 宾语从句必须用陈述语序。
False: He is wondering when can he finish this difficult job. Right: He is wondering when he can finish this difficult job. B 有时候可以用it 作形式宾语，而把真正的宾语从句放在后面。
Bad: I thought that he could finish this job in just two hours impossible. Good: I thought it impossible that he could finish this job in just two hours.