【(完整版)主语从句专项练习】在英语语法中，主语从句是一个重要的知识点，尤其在书面表达和考试中经常出现。掌握主语从句的结构与用法，有助于提高语言表达的准确性和复杂性。本文将围绕“主语从句”进行系统性的讲解，并提供一套完整的专项练习题，帮助学习者巩固相关知识。
一、什么是主语从句？
主语从句是指在句子中充当主语的从句。它通常由连接词（如 that, whether, if, what, who, when, where, why, how 等）引导，放在句首，作为整个句子的主语。例如：
- That he is late surprised everyone.
（他迟到让大家都很惊讶。）
在这个句子中，“That he is late”是一个主语从句，作整个句子的主语。
二、主语从句的常见引导词
1. that：引导陈述性内容，不充当句子成分。
- That she passed the exam is a big surprise.
2. whether / if：引导疑问性内容，表示“是否”。
- Whether he will come is still unknown.
3. what / who / when / where / why / how：引导具体的内容，相当于一个名词性从句。
- What he said made me angry.
- Where we went yesterday is a secret.
三、主语从句的语序
主语从句中的语序应为陈述语序，而不是疑问语序。例如：
- 正确：What he wants is a book.
- 错误：What does he want is a book.
四、主语从句的使用注意事项
1. 主语从句常用于正式或书面语中，口语中较少使用。
2. 有时可以用 it 作形式主语，把真正的主语从句后置，使句子更自然。
- It is clear that he is lying.
- It doesn’t matter whether you come or not.
五、主语从句专项练习题
一、选择题
1. ______ he will go to the party is not known yet.
A. That
B. If
C. Whether
D. What
2. ______ the meeting will start is still a question.
A. When
B. That
C. What
D. How
3. ______ she did not attend the meeting surprised us all.
A. That
B. Whether
C. Why
D. How
4. ______ you need help is obvious.
A. That
B. Whether
C. What
D. If
5. ______ he said at the meeting was very important.
A. That
B. What
C. Whether
D. How
二、填空题
1. ______ he left early made the meeting start late.
2. ______ the teacher said was very helpful.
3. ______ we should go there is still uncertain.
4. ______ they are coming is not clear.
5. ______ you need is time to think.
三、改错题
1. That he is late is surprising.
（错误：__________）
（正确：__________）
2. Whether he will pass the test is not sure.
（错误：__________）
（正确：__________）
3. What he did is not right.
（错误：__________）
（正确：__________）
4. How he got there is unknown.
（错误：__________）
（正确：__________）
5. That she is a teacher is true.
（错误：__________）
（正确：__________）
六、参考答案
一、选择题
1. A
2. A
3. A
4. A
5. B
二、填空题
1. That
2. What
3. Whether
4. Whether
5. What
三、改错题
1. 错误：That he is late is surprising.
正确：That he is late is surprising.（无错误，原句正确）
2. 错误：Whether he will pass the test is not sure.
正确：Whether he will pass the test is not certain.
3. 错误：What he did is not right.
正确：What he did is not right.（原句正确）
4. 错误：How he got there is unknown.
正确：How he got there is unknown.（原句正确）
5. 错误：That she is a teacher is true.
正确：That she is a teacher is true.（原句正确）
七、结语
通过本篇练习，希望同学们能够更好地理解和运用主语从句。在实际写作中，灵活运用主语从句可以提升语言的逻辑性和表达的多样性。建议多做相关练习，并结合例句进行分析，逐步提高语法运用能力。
