【表语从句专项指导练习】在英语语法中，表语从句是一种常见的从句类型，常用于对主语进行补充说明。它通常出现在系动词（如 be, seem, appear, become 等）之后，用来说明主语的性质、状态或身份。掌握表语从句的结构和用法，对于提高英语表达能力和写作水平具有重要意义。
一、什么是表语从句？
表语从句是指在句子中充当表语的从句，通常由连接词引导，放在系动词之后。它的作用相当于一个名词性短语，用来说明主语是什么、怎么样或者属于什么类别。
例如：
- The problem is that we don’t have enough time.
（问题是我们没有足够的时间。）
在这个句子中，“that we don’t have enough time” 是表语从句，修饰主语 “The problem”。
二、常见的引导词
表语从句常用的引导词有以下几种：
| 引导词 | 用法说明 |
|--------|----------|
| that | 不充当成分，仅起连接作用，常用于陈述事实 |
| whether / if | 表示“是否”，用于疑问情况 |
| who / whom / whose | 指代人 |
| what / which / when / where / why / how | 指代事物、时间、地点、原因、方式等 |
注意：在正式书面语中，一般使用 “whether” 而不是 “if” 引导表语从句。
三、常见句型结构
1. 主语 + 系动词 + that 引导的从句
- The fact is that he was late again.
- It seems that she is not coming.
2. 主语 + 系动词 + whether / if 引导的从句
- The question is whether we can finish the work on time.
- The issue is if he will support us.
3. 主语 + 系动词 + 疑问词引导的从句
- The problem is what we should do next.
- That’s where I left my keys.
四、易错点与注意事项
1. 不要混淆表语从句和宾语从句
宾语从句通常位于及物动词之后，而表语从句则紧跟在系动词后面。
- She said that she was tired.（宾语从句）
- She is that she was tired.（错误，应为表语从句：She is tired.）
2. 避免使用 “that” 引导的从句作表语时的冗余
如果主句已经有明确的形容词或名词作表语，就无需再加 “that” 引导的从句。
- 正确：He is a teacher.
- 错误：He is that a teacher.
3. 注意主谓一致和时态搭配
表语从句中的动词要根据主句的时态进行调整。
- The truth is that he has made a mistake.（现在完成时）
- The truth was that he had made a mistake.（过去完成时）
五、专项练习题
一、选择最佳答案：
1. The question is ______ we should go there tomorrow.
A. that
B. if
C. whether
D. what
2. What worries me is ______ he didn’t come to the meeting.
A. that
B. if
C. whether
D. why
3. The problem is ______ we can get the necessary materials.
A. that
B. if
C. whether
D. what
4. My opinion is ______ we should start early.
A. that
B. if
C. whether
D. what
5. The question is ______ the plan is practical.
A. that
B. if
C. whether
D. what
二、改写句子：
1. He is a student. → He is a student.
2. They are happy. → They are happy.
3. The reason is that he was sick. → The reason is that he was sick.
4. The answer is that it is correct. → The answer is that it is correct.
5. This is where we met. → This is where we met.
通过系统的练习和理解，表语从句的学习将变得更加轻松和高效。希望以上内容能帮助你更好地掌握这一语法点，并在实际应用中灵活运用。
