主语从句用法“大揭秘”

孙玉忠

主語从句是中学阶段的重点语法项目，也是高考的热点之一。主语从句在复合句中作主句的主语。其关系代词和关系副词有：that， whether， who， which， when， where， how， why等。

一、连接词的选择

按连接词的用法特点，我们可以把主语从句分为三类：

1. 以that引导的主语从句，尽管that没有实际意义，但也不能省略。如：

That she was wrong is obvious. 她错了，这是很明显的。

That we shall be late is certain. 我们将要迟到，这是显而易见的。

【注意】 有时可用形式主语 it 代替主语从句，即将it 放在句首，把主语从句放在句末，以避免句子头重脚轻。如：

It is doubtful whether he is coming. 他是否要来，是令人怀疑的。

It is hoped that the blacks will have equal rights. 我们都希望黑人能享有平等的权利。

2. whether 引导主语从句 ，不充当从句的任何成分。以whether（是否）引导的主语从句，不能用if来代替。如：

Whether they'll set out at 7：00 tomorrow morning is unknown. 明天他们是否要在7点出发，这是不知道的。

Whether she is coming or not doesn't matter too much. 她来不来都无关紧要。

【注意】 引导主语从句时只有用it作形式主语时，whether和if都能引导主语从句。如：

It hasn't been decided whether / if we shall attend the meeting. 我们是否去参加会议还没有决定下来。

3. who， which， what， why， when， how等引导主语从句

这类连接词也具有双重作用，翻译时这些连接词与其作疑问词的意思相当。有时也可用作形式主语it。如：

Which football team will win the match is unknown. 哪一个足球队会赢得比赛，还不清楚。

What we need now is more rest. 我们现在所需要的是更多的休息。

How the prisoner escaped is a completely wrong. 囚犯如何逃走的是一个绝对的错误。

【注意】

1. 如果带主语从句的句子是疑问句或感叹句时，则必须用形式主语it。如：

Is it true that the scientist will give us a talk next week？ 那位科学家下星期要给我们作报告是真的吗？

Has it been announced that when the planes are to take off？ 已经宣布飞机何时要起飞了吗？

How strange it is that the children are so quiet！ 真奇怪，这些孩子那么地安静！

2. what， whatever， whoever 等引导的主语从句，一般不用 it 作形式主语。如：

What he wants is a book. 他所想要的就是一本书。

Whoever leaves the room last should close the door. 无论是谁最后一个离开房间都要锁好门。

二、谓语动词的数

主语从句作主语，谓语动词一般用单数;但 what 引导的从句作主语，代表复数概念（常可从表语上看出）时，谓语动词则常用复数形式。如：

What we need is water. 我们所需要的是水。

What the boy wants are those red apples. 那个男孩想要的是那些红苹果。

三、主语从句中的语气

在下列情形中，主语从句的谓语动词用“should + 动词原形”。

1. It is suggested / requested / proposed / desired / required  that... ，主语从句中的谓语动词也要用虚拟语气。如：

It has been decided that the meeting （should） be put off. 已经决定推迟这个会议。

It is suggested that we （should） take the bus. 有人建议我们乘公共汽车。

2. 在用it作形式主语的时候，如果作表语的形容词为necessary， important， impossible， strange， natural， advisable， desirable， urgent， essential等时，即“It + be + 形容词 + 主语从句”，主语从句中的谓语动词要用虚拟语气，也就是“should+do”，should可以省略。如：

It is necessary that the problem （should） be discussed at once. 立刻讨论这个问题很有必要。

It is strange that he （should） have so many friends. 太奇怪了，他有那么多的朋友。

四、whoever， whatever， whichever引導主语从句

whoever， whatever， whichever可引导主语从句。Whoever = anyone who; whatever = anything what; whichever = anything which。whatever和 whichever还可用作连接形容词。如：

Whoever breaks the law should be punished. 无论是谁触犯了法律，都应受到惩罚。

Whatever was said here should be kept a secret. 这里说的话都应当保密。

Whichever book she bought would be paid for. 无论她买了哪一本书都要付款。

五、强调句中的主语从句

为了达到某种表达效果，主语从句有时可用在强调句中。如：

It was what she said that made all the people present laugh. 就是她说的内容让在场的人都大笑起来。

【考点精练】

I. 单句语法填空。

1. It suddenly occurred to him ___ he had left his keys in the office.

2. The limits of a person's intelligence， generally speaking， are fixed at birth， but ___ he reaches these limits will depend on his environment.

3. It doesn't matter ___ you turn right or left at the crossing—both roads lead to the park.

4. It is by no means clear ___ the president can do to end the strike.

5. Most of what has been said about the Smiths ___ （be） also true of the Johnsons.

6. It is required in the regulations that you

___ （tell） other people the password of your e-mail account.

7. As many five courses are provided， and you are free to choose ___ suits you best.

II. 从方框中选择合适的词填空（方框中的单词数量可能多， 有的词也许不是用一次）。

what， who， that， whether， because， if， where， when， why， how， whomever， whatever， whichever，  whoever

1. ___ you don't like him is none of my business.

2. After Yang Liwei succeeded in circling the earth， ___ our astronauts desire to do is walk in space.

3. ___ leaves the room last ought to turn off the lights.

4. ___ he can finish his task on time is of great importance.

5. ___ they will solve the serious problem has not been decided.

6. ___ he did that wasn't quite clear.

7. ___ he said at the meeting astonished everybody present.

8. It is a fact ___ the English is being accepted as international language.

9. ___ the old man comes from is still a puzzle.

10. It won't make too much difference___ he will join us.