宾语从句的特点:
1.宾语从句可以作及物动词、介词及形容词的宾语。
2.宾语从句的语序一律用陈述句语序。
3.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。
4.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。
5.如果从句太长，可以用形式宾语it.

宾语从句的时态:
1.主句是一般现在时，从句根据实际情况使用任何时态。
例句：The headmaster hopes everything goes well.
2.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.
3.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.
4. 如果从句的动作发生在主句之前，则从句要用过去完成时态。 

宾语从句的语序:
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.　 
C. 带有宾语从句的复合句的否定形式一般是否定主句。
Bad: I think he doesn’t like the English teacher. 　　
Good: I don’t think he likes the English teacher. 
D.  主句一般过去时态，从句也要用过去时态。
False: He wanted to know why he is crying in the corner. 　　
Right: He wanted to know why he was crying in the corner

宾语从句的否定转移:
主句的谓语动词是think,believe,imagine,suppose,consider,espect,fancy,guess等。
并且主句的主语是第一人称而且为一般现在时，从句的否定词一般要转移到主句上来,其反义疑问句一般与宾语从句一致。
I don’t think he will come to my party.而不能说成I think he won’t come to my party.
我认为他不会来我的舞会.
I don’t believe that man is killed by Jim,is he?
我认为那个人不是Jim所杀的,是不是?
如果宾语从句中有某个含有否定意义的形容词或副词,其反义疑问句要用肯定形式。
We find that he never listens to the teacher carefully,does he?
我们发现他从来不仔细听老师讲课，是不是?

宾语从句中引导词的用法比较
在复合句中作主句的宾语，引导词有：
连词：that (that 常可省略),whether, if
代词：who, whose, what ,which
副词：when ,where, how, why 等。

（一）that引导的宾语从句（在非正式场合that可以省略）
1.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.

2.在以下情况中that不能省略
a.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.
b.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.
c.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.
d.注: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.

（二）由whether,if 引导的宾语从句
1.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.

2.只能用whether，不能用if引导的宾语从句
a.在带to的不定式前
例句：We decided whether to walk there.
b.在介词的后面
例句：I’m thinking of whether we should go to see the film.
c.在动词后面的宾语从句时
例句：We discussed whether we had a sports meeting next week
d.直接与or not连用时
例句：I can’t say whether or not thet can come on time.

3.只能用if不能用whether引导的宾语从句
a.if引导条件状语从句，意为“如果”
例句：The students will go on a picnic if it is sunny.
b.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.
c.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.

if,whether在宾语从句中的区别
a.if和whether在作“是否”解时,引导宾语从句常放在动词know,ask,care,wonder,find out等之后,介词后一般不用if
b.少数动词,如:leave,put,discuss,doubt后的宾语从句常用whether. 
c. whether后可以加or not,但是if不可以.
d.在不定式前只能用whether.
（如：I can’t decide whether to stay. 我不能决定是否留下。）
e.避免歧异时,我们常用whether而不用if.

（三）连接代词和连接副词引导的宾语从句
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。
1.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?
2.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.

简化宾语从句常用六法：
方法一：
当主句谓语动词是hope， decide， wish， choose， agree， promise等，
且宾语从句的主语与主句主语一致时，宾语从句可简化为不定式结构。
例如：
Li Ming hopes he will be back very soon.
→Li Ming hopes to be back very soon.
We decided that we would help him.
→We decided to help him.

方法二：当主句谓语动词是know， learn， remember， forget， tell等动词，
且主句主语与从句主语一致时，宾语从句可简化为“疑问词+不定式”结构。例如：
She has forgotten how she can open the window.
→She has forgotten how to open the window.
注：当主句谓语动词是tell， ask， show， teach等动词，
且后带双宾语，从句主语和间接宾语一致时，宾语从句可简化为“疑问词+不定式”结构。例如：
Could you tell me how I can get to the station？
→Could you tell me how to get to the station？

方法三：当主句的谓语动词是order（命令），require（需要）等时，
如果主句和从句的主语不一致，宾语从句可简化为“名词（代词）+不定式”结构。例如：
The headmaster ordered that we should start at once.
→ The headmaster ordered us to start at once.

方法四：某些动词后的宾语从句，可以用介词加动名词（短语）等其他形式简化。例如：
He insisted that he should go with us.
→He insisted on going with us.
The poor boy doesn’t know when and where he was born.
→The poor boy doesn’t know the time and the place of his birth.

方法五：某些动词后面的宾语从句可转化为“宾语+V-ing形式（作宾语补足语）”结构。例如：
Liu Ping found that there was a wallet lying on the ground.
→ Liu Ping found a wallet lying on the ground.

方法六：动词seem后的宾语从句，也可以用不定式（短语）来简化，但句型需要进行适当的变化。例如：
It seemed that the boys were going to win.
→The boys seemed to win.
除上述方法外，还有一些特殊句式的转化。例如：
I found that it was difficult to learn English well.
→I found it difficult to learn English well.
Soon we found that the ground was covered with thick snow.
→Soon we found the ground covered with thick snow.
They found that the box was very heavy.
→They found the box very heavy

省略现象：
一、单词省略
1、省略介词
He spent four hours (in) going over his lessons. 他花了四个小时复习功课。
I ' ve studied Eng1ish (for) five years. 我已学五年英语了。
2、省略连词 that
I believe (that) you will succeed ． 我相信你们会成功的。
It ' s a pity (that) he ' s leaving. 他要走，真遗憾。
I ' m sure (that) she will help you. 我肯定她会帮你的。
3、省略关系代词
I ' ll give you all (that) I have. 我要把我所有的一切都给你。
He read the book (which) I got yesterday. 他看过我昨天买的书了。

二、句子成分的省略
1、省略主语
Beg your pardon.
（我）请你原谅。（ Beg 前省略了主语 I ）
Take care!
当心！（ Take 前省略了主语 you ）
Looks as if it will rain.
看起来象要下雨。（ Looks 前省略了主语 it ）
2、省略谓语
Who next?
该谁了？（ Who 后面省略了谓语 comes ）
The river was deep and the ice thin.
（ ice 后面省略了 was ）
We ' ll do the best we can.
我们将尽力而为。（ can 后面省略了动词 do ）
3、省略表语
Are you ready? Yes, I am.
你准备好了吗？ 我准备好了。（ am 后面省略了 ready ）
He was a lover of sports as he had been in his youth.
他还是象年轻时那样，是一位运动爱好者。（ had been 后面省略了 a lover of sports ）
4、省略宾语
Let ' s do the dishes. I ' ll wash and you ' ll dry.
让我们洗碗吧，我来洗，你来揩干。（ wash 和 dry 后面省略了宾语 dishes ）
5、省略定语
He spent part of the money, and the rest he saved.
那钱他花了部分，其余的他都存了起来。（ the rest 后面省略了定语 of the money ）
6、省略状语
He was not hurt. Strange!
他没有受伤，真奇怪！（ Strange 前面省略了状语 how ）

三、不同句式中的省略
 1. 简单句中的省略：
在对话中，交谈双方都知道谈论的对象，则可以省略句子的主语，省略主语和谓语的现象在交际用语中出现的很多。
（1）Looks like rain.
（2）Hope to hear from you soon.
（3）Sounds like a good idea.
2. 并列句中的省略：
在并列句中，相同的成分如主语，谓语，宾语等都可以省略：
（1）They learn French and we English.
（2）My father planned and built all these houses.
（3）John won the first race and Jimmy the second.
3. 复合句中的省略：
定语从句：
That’s the reason he is late for the conference.
状语从句：
（1）If heated, water will boil.
（2）Tom was attacked by cramp while swimming across the river.
宾语从句：
如果宾语从句中的谓语部分与主句的谓语部分或上文的谓语部分相同，可将从句部分的谓语省略。
We will do what we can（do）to help you.
—Is Mr. King in his office?
 —Sorry, I don’t know（whether he is in his office or not）.
4. 动词不定式的省略：在动词不定式结构中，为了避免重复，常常省略不定式结构中的动词原形，只保留to。
—Would you like to go with us ?
 —I’m glad to, but I have to finish my homework.
在used to, ought to, have to, would like/love to, wish to, be going to等结构中，常常省略to后面的动词原形。
（1）They do not visit their parents as much as they ought to.
（2）He doesn’t get up early as he used to.
（3）I’ll hand it in if I have to.
（4）
—Would you like to come tonight ?
—I’d love to.
Tell , warn , order , advise , ask等动词的宾语后面接动词不定式做宾语补足语时，可以省略to后面的动词原形。
（1）He wanted to swim across the river but I warned him not to.
（2）The boy wanted to play football in the street, but his mother told him not to.