从句讲解
宾语从句：1.宾语从句在句中作及物动词或介词的宾语，从句放在主句之后，前后不用逗号分开。
2.引导宾语从句的词有：
连词that(在口语中that常可省略)，if, whether,如：
He knows that Jim will work hard.
连接代词who, whom, which等，如：
Do you know who (whom) they are waiting for?
连接副词when, where, how, why等，如：Could you tell me how we can get to the station?
3.whether和if都有“是否”的意思，一般情况下两者可以换用，但在介词之后，
不定式之前，与or not连用，在句首或在引导表语从句，同位语从句时，只能用whether,如：I want to know if/whether the news is true. He doesn't know whether to stay or not?
4.宾语从句要用陈述句语序。
5.宾语从句一定要注意时态呼应，即：当主句谓语动词是过去式时，从句中谓语动
词也要用过去范畴的时态，但若从句陈述的是真理或客观规律，其谓语的时态仍用一般现在时，如：
He asked who could answer the question.
My father told me that the earth goes around the sun.
6.一个宾语从句只能用一个连词。
7.当主句谓语动词是think, believe等动词时，宾语从句的否定意义要放到主句中。另外，当主句主语为第一人称时，后面若接附加疑问句，那么附加疑问句的主语、谓语应与从句中的主谓语保持一致。如：
I don't think he looks like his father, does he?
8.直接引语和间接引语也是宾语从句，直接引语是引述别人的原话，放在引号内，
不用连词联接；间接引语是用自己的话转述别人的话，通常用连接词与主句联接。
(1)陈述句变为以that引导的宾语从句，如：
He said,“I'm happy.”[FY()[FY]]He said that he was happy.
(2)一般疑问句变为if(whether)引导的宾语从句，如：
He asked me,“Does his father know Mr Green?”
---He asked me if his father knew Mr Green.
(3)特殊疑问句变为由who, what, where, how等疑问词(连接代词或连接副词)引导的宾语从句，如：
He asked me,“Where is Mr Wang?”
---He asked me where Mr Wang was.
注意上述例句中连词、时态、语序等变化 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 18.2 关系副词引导的定语从句
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。
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.
表语从句
一 定义：
A 表语从句就是用一个句子作为表语。
The problem is puzzling.
主语 连系动词 形容词作表语
The problem is when we can get a pay rise.
主语 连系动词 一个句子作表语---表语从句
B 连接表语从句的连接词有：that, what, who, when, where, which, why,
whether,how.
He has become a teacher.
He has become what he wanted to be ten years ago.
She has remained there for an hour.
She has remained where I stood yesterday for an hour.
His suggestion is good.
His suggestion is that we should stay calm.
The question is confusing.
The question is when he can arrive at the hotel.
who will travel with me to Beijing tomorrow.
why he cried yesterday.
how I can persuade her to join us in the party.
whether the enemy is marching towards us.
二 注意：
A 表语从句一定要用陈述语序。
False: The question is when can he arrive at the hotel.
Right: The question is when he can arrive at the hotel.
B 不可以用if，而用whether 连接表语从句(as if 例外）。
False: The question is if the enemy is marching towards us.
Right: The question is whether the enemy is marching towards us.
Right: It looked as if he had understood this question.
C 不像宾语从句，在有表语从句的复合句中，主句时态和从句时态可以不一致。
Right: The question is who will travel with me to Beijing tomorrow.
Right: The question is why he cried yesterday.
D that在表语从句中不可以省掉。
表语从句只能置于主句之后，而主句的动词只能是联系动词。