Idon’t think (that) there will be time to do it.
Manypeoplebelievethatrobotswilldo most of our work.
whether/if引导的宾语从句
1）可用whether/if的情况
whether/if常放在ask, care, wonder, find out等后引导宾语从句。whether/if在从句中不作成分，但是有“是否”含义，不可省略。
It occurred to me that we should get in touch with the manager.
whether/if引导的主语从句
whether引导的主语从句即可以放在句首，也可以放在句末，但if引导的主语从句只能放在句末，前面需用it作形式主语。whether，if只起连句中不作成分，且不可省略。
Iaskedthem whether/if they would win the match.
Do you care whether/if you win?
2)只用whether不用if的情况
引导介词后的宾语从句时。
Itdepends on whether it will snow tomorrow.
Wedoubt whether he will keep his promise.
宾语从句前置，置于句首时。
Whetherthey can come here on time, we don’t know.
连接代词或连接副词引导的主语从句
1）连接代词what, who, whom, , whose, which , whatever, whoever, whichever等在从句中作主语、宾语、表语、定语,不可以省略。
连接代词或连接副词引导的主语从句
1）连接代词what, who, whom, , whose, which , whatever, whoever, whichever等在从句中作主语、宾语、表语、定语,不可以省略。
Whathe said just now is true.
Who breaks the law will be punished.
e.g. It is suggested that you(should) spend more time in studying English.
4It+动词（+宾语或状语）+that从句。
常用于这种结构的动词有：
seem
显得
happen
碰巧
matter
重要
occur
出现
turn out
结果是
Ithappened to me that I was away when he called.
名词性从句
概念
在复合句中起名词作用的从句叫作名词性从句。
种类
主语从句、宾语从句、表语从句和同位语从句。
注：由于名词性从句在句中不同的句法功能（即名词性从句在复合句中，能充当主语、宾语、表语、同位语等。），相应地，名词性从句可以分为主语从句、宾语从句、表语从句和同位语从句。
引导词
类别
功能
例词
从属连词
指起连接作用，不充当从句中的任何成分
据说
told
有人告诉
heard
有人听说
reported
据报道
decided
作出决定
suggested
有人建议
advised
有人建议
ordered
根据命令
remembered
有人记得
thought
有人认为
considered
认为
well-known
很著名
hoped
有人希望
announced
据宣布
Itis reported that no passengers were injured in the accident.
Whatthey need are a car and some water.
（acar and some water表示复数概念，谓语动词用复数）
2）连接副词when, where, why, how，whenever，however，wherever等在从句中作状语。
Why they suddenly disappeared remains a mystery.
注：It is necessary/important/surprising/strange/unthinkable/unbelievable/incredible that+主语(should)+动词原形+其它。
e.g. It is necessary that a college student (should) master one or two foreign languages.
We’re all pleased that we have once again overcome the difficulty.
I am extremely sorry that I have troubled you so much.
that引导的宾语从句
that引导的宾语从句表示陈述意义。that无实际意义，在从句中不充当任何成分。that可以省略。
注： whoever和whatever引导的名词性从句一般不用it作形式主语。
what引导的主语从句一般按单数对待，但在实际使用中，其单复数取决于其成分的含义。
e.g. What the kid wanted was only a new school bag.
（schoolbag是可数名词单数，谓语动词用单数）
注：从句作主语，谓语动词用单数形式。
2)在that引导的主语从句中，常用it作形式主语，that引导的真正的主语从句后置，常见的此类句型有：
1It+系动词+形容词+that从句。
常用于这种结构的形容词有：
necessary
必要的
certain
明确的
right
正确的
clear
清晰的
(un)likely
I don’t know whom you should depend on.
Could you tell me which gate we have to go to?
2)连接副词when, where, why, how，whenever，however，wherever等在从句中作状语。
Hedidn’t tell me when the traffic accident had taken place.
It is strange that you (should) trust Jane.
2It+系动词+名词+that从句。
常用于这种结构的名词有：
a pity
遗憾
a honor
荣耀
a shame
令人遗憾的事
a wond
no wonder
难怪
a fact
事实
no surprise
可以运用it作形式宾语代替宾语从句
A.动词find, feel, think, consider, make, believe, guess, suppose, assume等后有宾语补足语时，要用it作形式宾语，而把that引导的宾语从句后置。
e.g. I think it necessary that we take plenty of hot water every day.
Weare talking about whether we admit students into our clubs.
They look similar except that one is a little tall.
3)作系表结构的宾语。
常用于此类结构的形容词有：sure, certain, glad, pleased, happy, afraid, surprised, satisfied, sorry等表示“情感”的形容词。
Whetheryou can succeed or not depends on how hard you work at it.
（whether引导的主语从句放在句首）
It is unknown whether/if he has agreed to my plan.
（主语从句是whether/ifhehas agreed to my plan, it作形式主语）
that, whether, if
连接代词
既起连接作用，本身又作从句的主语、宾语、表语或定语
who, whom, whose, which, what, whoever, whatever, whichever
连接副词
既起连接作用，本身又作从句的状语
when, where, how, why，whenever，wherever，however
与ornot连用时。
Iaskedyour secretary whether she could come or not.
与不定式连用时。
Ireallydon’t want know whether to accept or refuse.
有些动词，如leave,put, discuss, doubt等后的宾语从句常用whether引导。
主语从句
主语从句可直接放在句首，也可用形式主语it代替，而将主语从句后置。
that引导的主语从句
1)that引导的主语从句置于句首（that此时在从句中不充当任何成分，无含义，只起连接作用，不能省略）