宾语从句是名词性从句的一种。在主从复合句中充当宾语，位于及物动词、介词或复合谓语之后的从�
I don’t know what they are looking for.
Could you tell me when the train will leave?
Can you imagine what kind of man he is?
可跟that从句做宾语的动词有：
say, think, insist, wish, hope, demand, imagine, wonder, know, suppose, see, believe, agree, admit, deny, expect, explain, order, command, feel, dream, suggest, hear, mean, notice, prefer, request, require, propose, declare, report等。
例句：The boy believes that he will travel through space to other planets.
注意事项：当主句谓语动词是 think, believe, suppose, expect 等词，而宾语从句的意思是否定时，常把否定转移至主句表示。
例句：I don’t think it is right for him to treat you like that.
在以下情况中that不能省略
当句中的动词后接多于两个由that引导的宾语从句时，第一个that可省，但后面的that不可省。
例句：He said (that) you were too young to understand the matter and that he was asked not to tell you.
当主句的谓语动词与that宾语从句之间有插入语时，that一般不可省。
例句：Just then I noticed, for the first time, that our master was wearing his fine green coat and his black silk cap.
当that从句是双宾语中的直接宾语时，that不可省。
例句：I can’t tell him that his mother died.
注意事项：许多带复合宾语的句子，that引导的宾语从句经常移到句子后部，而用it作形式宾语。
例句：I find it necessary that we should do the homework on time.
1. that:没有含义，在宾语从句中不做成分
2.whether/if:表示是否，在宾语从句中不做成分。
I don't know if /whether he still lives here after so many years. 我不知道这么多年后，他是否还住在这里。
3.连接代词：what, which, who, whom, whose(在宾语从句中做主、宾、表和定语)
连接副词：where, when, how, why(在宾语从句中做状语)
The small children don't know what is in their stockings.(what 在宾语从句中做主语)
这些小孩子不知道什么在他们的长筒袜里。
Could you tell me why you were late for the meeting this morning?(why 在宾语从句中做原因状语)
你能告诉我为什么你今天早上开会迟到吗？
由whether(if)引导的宾语从句，实际上是一般疑问句演变而来的。意思是“是否”。宾语从句要用陈述句语序。一般说来，在宾语从句中whether与if可以互换使用，但在特殊情况下if与whether是不能互换的。
例句：I wonder whether(if) they will come to our party.
只能用whether，不能用if引导的宾语从句
在带to的不定式前
例句：We decided whether to walk there.
在介词的后面
例句：I’m thinking of whether we should go to see the film.
在动词后面的宾语从句时
例句：We discussed whether we had a sports meeting next week
直接与or not连用时
例句：I can’t say whether or not thet can come on time.
只能用if不能用whether引导的宾语从句
if引导条件状语从句，意为“如果”
例句：The students will go on a picomic if it is sunny.
if引导否定概念的宾语从句时
例句：He asked if I didn’t come to school yesterday.
引导状语从句even if（即使）和as if（好象）时
例句：He talks as if he has known all about it.
这样的宾语从句实际上是由特殊疑问句变化而来的，宾语从句要用陈述句语序。用于这种结构的动词常常是：see, say, tell, ask, answer, know, decide, show, find out, imagine, suggest, doubt, wonder, discover, understand, inform, advise等。
英语中的连接代词有：who,whom,whose,which,what,在句中担任主语、宾语、定语或者表语。
例句：Can you tell me whom you are waiting for?
英语中的连接副词有：when,where,why,how，在句中担任状语的成分。
例句：None of us knows where these new parts can be bought.
1. 时态
①当主句是现在时态时，宾语从句可以根据需要使用任何时态。
I don't know when he will come back.我不知道他将何时回来。
He tells me that his sister came back yesterday.他告诉我他姐姐昨天回来了。
②当主句是过去时态时，宾语从句必须是一种过去的时态。
She asked me if I knew whose pen it was.她问我是否知道这是谁的钢笔。
He said that he could finish his work before supper.他说他会在晚饭前完成工作。
③当表示客观事实或普遍真理的句子做宾语从句时，任何时候都用一般现在时。
The teacher said that the earth goes round the sun.老师说过地球绕着太阳转。
2. 语序
任何从句都使用陈述句语序，宾语从句当然也不例外。
1. 动词宾语从句：顾名思义，它是位于动词后面的宾语从句。
例如：He asked whose handwriting was the best in our class.他问我们班上谁的书法最好。
2. 介词宾语从句：顾名思义，它是位于介词后面的宾语从句。
例如：I agree with what you said just now.我同意你刚才说的话。
3. 形容词宾语从句：顾名思义，它是位于形容词后面的宾语从句。
例如：I am afraid that I will be late. 恐怕我要迟到了。
置于动词、介词等词性后面起宾语作用的从句叫宾语从句。宾语从句的语序必须是陈述语序。谓语动词、介词、动词不定式，v.-ing形式后面都能带宾语从句。有些形容词（afraid,sure,glad等）之后也可以带宾语从句。
宾语从句的语序一律用陈述句语序。
连接词that引导宾语从句在句中无词义，不充当句子成份，多数情况下可以省略。
whether 和 if 都可引导宾语从句，但 whether后可紧跟or not;whether从句可作介词的宾语。
如果从句太长，可以用形式宾语it.
在整个句子中做宾语的从句叫做宾语从句。
如：She knew that the teacher had seen the film.
她知道这位老师看过这部电影。
(“that the teacher had seen the film”做 knew 的宾语，同时又是由连接词 that 引导的从句，所以它叫做宾语从句。)
例句：The headmaster hopes everything goes well.
主句是过去时态，从句须用过去时态的某种形式。
例句：She was sorry that she hadn’t finished her work on time.
当宾语从句表示的是一个客观真理或者事实时，即使主句是过去时，从句也用一般现在时态。
例句：The teacher told his class that light travels faster than sound.
连词：that （that 常可省略），whether, if
代词：who, whose, what ，which
副词：when ，where, how, why 等。