名词性从句
引导名词性从句的连接词主要有三类：
▪ 连接词： that, whether, if, as if/though。That用来引导陈述句，本身没有意义，在宾语从句或表语从句中一般可以省略；但在介词之后或引导主语从句和同位语从句时，that不能省略。Whether和if引导一般疑问句（从句中的一般疑问句要用陈述句语序）。As if/though引导表语从句。
▪ 连接代词：who, whom, whose, what, which, whatever, whichever, whoever等。该类词由于在从句中作相应的句子成分，因此一般不能省略。
▪ 连接副词：when, why, how, where等。该类词一般也作相应的句子成分。
一、主语从句
1. 主语从句是在复合句中作主语的从句。主语从句一般出现在句首，谓语动词之前。许多情况下，为了平衡句子结构，常用it代替主语从句，将主语从句后置，it只是形式主语。
When he will be back is still unknown. 他什么时候回来还不知道。
Whoever comes is welcome. 不论谁来都欢迎。
What (=The thing that) many people haven’t realized is that Simon is a love of sports, and football in particular.
很多人所没有意识到的是，西蒙是运动爱好者，尤其爱足球。
How this happened is not yet clear. 这事怎么发生的，尚不清楚。
It has not been decided where the meeting is to be held. 在哪里开会还没决定。
It is not important who will go. 谁会去，这不重要。
*注意：由连接代词what, whatever, whoever等引导词的主语从句一般不能用it作形式主语。如：
What he found surprised me greatly. 他的发现使我非常吃惊。
Whoever is finished may rest. 凡是做完的人都可以休息。
2. whether 与 if 引导主语从句的区别：
▪ whether 引导的主语从句既可放在句首也可放在句首也可放在句尾，if 引导的主语从句只能放在句末；
▪ whether 后面可跟or或or not，其中or not既可紧跟在whether之后，也可放在句末或者省略，而if后面通常不接or not，如要接，则需与if分开后放在后面。
Whether she comes or not makes no difference. 她来比来都没有关系。
It is doubtful whether/if the President knew the details of the plan.
总统是否知道这个计划的细节，这一点颇有疑问。
二、宾语从句
1. 宾语从句在句中作及物动词或介词的宾语。某些系表结构的形容词有及物动词的作用，其后可接宾语从句，该类形容主要有：certain, afraid, sure, anxious, aware, glad, proud, surprised, worried, sorry, ashamed, determined, pleased, satisfied, annoyed, disappointed等。
I doubt whether he will come. 我怀疑他是否会来。
Whether you will succeed or not depends on what you do and how you do it.
你是否会成功，取决于你做什么和怎么做。
She assured us that everything would turn out all right. 他向我们保证一切会很顺利。
I’m afraid that I have made a mistake. 恐怕我已经犯了一个错误。
I’m not sure whether we can stop him from smoking. 我不确定我们是否能阻止他抽烟。
Eg. After _____seemed an endless wait, it was his turn to enter the personnel
manager’s office.
A that B it C what D there
2. it 形式宾语
▪ 在宾语复合结构“及物动词+宾语+宾补”中，往往用形式宾语it替代宾语从句，将真正的宾语从句后置，即“及物动词+it+宾补+宾语从句”；
▪ 大多数介词不能直接跟that从句作宾语，这时一般需要it作形式宾语，作为真正宾语的that从句后置，that不可省略。
We consider it necessary that you have a clear understanding of the situation.
我们认为你有必要认清形势。
You may rely on it that I shall help you. 你可以指望我会帮助你。
3. 在介词in, except, save, besides和but之后可以跟that从句，但看作固定用法：in that, expect that, but that, save that, besides that。
4. whether 和if 引导的宾语从句可以互换使用，但介词后的宾语从句只能用whether，不能用if。
I don’t care whether/if they are following my advice. 我不介意他们是否听从我的建议。
It is a question of whether we should go. 问题是我们是否应该走。
5. 宾语从句中连词that通常可以省略，但以下情况不可省略连词that。
(1) 当主句谓语动词后接两个或两个以上宾语从句时，除第一个从句外，其他从句的that不易省略。如：
The teacher told the student (that) they should hand in their homework on time and that they would have a test the next day.
老师告诉学生，他们应该按时交作业，并且第二天他们会进行考试。
(2) 当主句与that引导的宾语从句之间有插入语时，that不能省略。如：
He didn’t know, I’m sure, that John was going to America. 我确信他不知道约翰要去美国。
(3) 当宾语从句是复合句，且该复合句的从句位于主语之前时，that不能省略。如：
He promised that if he came back early, he could cook for her.
他承诺说，他如果回来得早，就会给她做饭。
(4) 当that 宾语从句是双宾语中的直接宾语时，that一般不能省略。如：
I will never tell anyone that you have ever been there. 我不会告诉任何人，你曾
经到过这里。
(5) 当it作形式宾语，that引导的宾语从句后置，that不能省略。如：
She makes it clear that the meeting won’t be put off. 她明确表示会议不会推迟。
三．表语从句
1. 表语从句在句中作表语，位于主句中的系动词之后。
The question is who can complete the difficult task. 问题是谁能完成这项艰巨的任务。
2. 表语从句可用whether引导，也可用as if/though引导，但不能用if引导。
He looked as if he was going to impress everything in the room into his mind.
他看上去像是把屋里的一切都印入脑海。
His first question was whether Tom had arrived yet. 他的第一个问题是汤姆是否已经到了。
3. 当主句的主语是reason时，表语从句的引导词要用that， 不能用because。
区分以下形式：
▪ That’s why+结果；
▪ That’s because+ 原因；
▪ The reason why/for... Is/was that...
He is careless and irresponsible. That was why he was dismissed.
他既粗心又不负责任，这就是他被解雇的原因。
He was dismissed. That was because he is careless and irresponsible.
他被解雇的了，这是因为他既粗心又不负责任。
The reason why he was dismissed was that he was is careless and irresponsible.
他被解雇的原因是他既粗心又不负责任。
四．同位语从句
1. 同位语从句就是跟在名词后面，表达具体内容、起解释说明作用的从句。
下列名词后面可接同位语从句：
hope, fact, news, message, problem, conclusion, rumor, agreement, belief,
concept, idea, question, suggestion, thought, conviction, doubt, decision, assumption, evidence, promise等。
引导同位语从句的词通常有连词 that, whether，连接副词 how, when, where, why等。That引导同位语从句时通常不可省略；if和which不能引导同位语从句。如：
The news that I have passed the exam is true. 我通过考试的消息是真的。
I have no idea why she cries. 我不知道她为什么哭。
I have no idea when he will be back. 我不知道他什么时候能回来。
We are not looking into the question whether he is worth trusting.
我们不是在调查“他是否值得信赖”这个问题。
I made a promise that if anyone set me free I would make him very rich.
我曾许诺，如果谁让我自由，我就让他非常富有。
2. 有时同位语从句不紧跟在它所说明的名词后，而被别的词语隔开。
The thought came to her that maybe she had left the door open when she left home.
她突然想起她可能在离开家时没把门关上。
3. doubt在否定句中带同位语从句时的引导词通常是that；在肯定句中则一般用whether。
There is some doubt whether he will come on time. 人们怀疑他是否会准时来。
I don’t doubt at all that he will finish it on time. 我绝对相信他会按时完成任务的。
Eg. There is no doubt _____the couple did the right thing in coming back earlier than planned.
A whether B that C why D when
练习
1. Which of the following italicized parts(斜体部分）is a subject clause(主语从句）?
A. We are quite certain that we will get there in time.
B. He has to face the fact that there will be no pay rise this year.
C. She said that she has seen the man earlier in the morning.
D. It is sheer luck that the miners are still alive after days.
2. The team can handle whatever________.
A that needs handling B which needs handling
C it needs handling D needs to be handling
3. Quality is_____counts most.
A which B that C what D where
4. The government has promised to do_______lies in its power to ease the hardship of the victims in the flood-stricken area.
A however B whichever C whatever D wherever
5. After ______seemed an endless wait, it was her turn to enter the personnel manager’s office.
A that B there C what D it
6. He’s _______as a “bellyacher”—he’s always complaining about something.
A who is known B whom is known
C what is known D which is known
7. She managed to save ______she could out of her wages to help her brother.
A how little money B so little money
C such little money D what little money
8. There is no doubt _____the company has made the right decision on the sales project.
A why B that C whether D when
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