以下是小编整理的主语从句的讲解，希望对大家有所帮助
主语从句三要点
[寻规找矩]
请观察下列句子，注意划线部分句子的意义及用法。
1. What surprised me most was that the little girl could play the violin so well.
2. Who will go to the concert is not known.
3. That she was chosen made us very happy.
4. Whether she will come or not is still a question.
5. Which book they will choose is still unknown.
6. When we shall hold our sports meet is not decided.
7. It’s strange that he knows nothing about it.
8. It is a pity that she has made such a mistake.
9. It is said that President Jingo will visit our school next week.
[小结归纳]
(一)语序
主语从句使用陈述语序，其通常结构为“引导词 + 主语 + 谓语 + 其他成分”;但当连接代词同时充当从句主语时，其结构为“连接代词 + 谓语 + 其他成分”，如句1、2。
(二)引导词
① that引导主语从句时无词义，也不充当任何成分，但通常不可以省略，如句3;
② whether引导主语从句时意为“是否”，通常不能用if来代替,如句4;
③ 可以引导主语从句的连接代词主要有：who, whom, whose, what, which, whatever, whoever等，如句5;
④ 可以引导主语从句的连接副词主要有：where, when, how, why等，如句6。
(三)常见句型
有时为避免句子头重脚轻，常用it作形式主语，代替主语从句放在句首，而把主语从句置于句末。常用句型如下：
① It + be + 形容词 + that 从句， 如句7;
② It + be + 名词 + that 从句， 如句8;
③ It + be + 动词的过去分词 + that 从句， 如句9。
主语从句学习指导
[寻规找矩] 请观察下列句子，注意主语从句的用法。
1. That the earth travels round the sun is a well-known fact.
2. It is uncertain whether the artist can do it or not.
3. Who will act the lead in the play has not been decided yet.
4. Where the young man has gone is not known.
5. It is not yet decided when and where the test will be given.
[归纳总结]
1. 引导主语从句的词有连词that, whether;连接代词who, whose, whom, whoever, what, which等;连接副词where, when, whenever, wherever, how, why等。
2. 有时用it作形式主语，将主语从句后置。
[常见错误展示] 下列各句均有一处错误，请改正并分析错误的原因。
1. Light travels faster than sound is common knowledge.
2. If she’s coming or not doesn’t matter much.
3. That the professor said is of great importance.
4. Where will the trees be planted has not been decided.
5. No matter who breaks the rule will be punished.
6. When and where the meeting will be held still remain a question.
7. What were your problems a year ago has now become mine.
8. It was requested that everyone made a speech at the meeting.
[解析与拓展]
1. 在句首加That(并将Light改为light)。that虽无词义但引导主语从句位于句首时不能省略。
2. 将If改为Whether。if, whether都可表示“是否”，但if不能引导位于主句之前的主语从句，它可以引导位于主句之后带有形式主语it的主语从句。
3. 将That改为What。that引导主语从句时无词义。What the professor said表示“教授所说的”。
4. 将will置于trees之后。主语从句要用陈述句语序。
5. 将No matter who改为Whoever。引导让步状语从句时二者可互换，但引导名词性从句时只能用whoever。
6. 将remain改为remains。主语从句表示单一概念时，谓语要用单数形式。
7. has要改为have。主语从句表示复数概念时，谓语要用复数形式。
8. 将made改为(should) make。在“It is requested / ordered / suggested + that从句”中，从句要用虚拟语气，即谓语用“should + 动词原形”，should可省略。
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