通过大量例句掌握主语从句、宾语从句、表语从句的构成与用法
一、什么是名词性从句？
名词性从句（Noun Clauses）是指在句中充当名词性成分（主语、宾语、表语、同位语）的从句。常由 that, whether, if, what, how, when, why, where, who, whom, whose, which 等引导词引出。
二、主语从句（Subject Clause）
在句子中做主语的位置，常用 That… 引导。
✔ That he passed the exam surprised everyone.
👉 译：他通过考试让大家都很惊讶。
✅ 主语从句通常用于书面语，口语中常用 It 形式替代主语：
✔ It is surprising that he passed the exam.
三、宾语从句（Object Clause）
名词性从句最常见的用法是作宾语，用于及物动词、介词后。
- 陈述句用 that 引导（that 可省略）：
✔ I think (that) she is right.
✔ We know that he will come back. - 一般疑问句变 if / whether 引导：
✔ I don’t know if he will attend.
✔ She asked whether it was true. - 特殊疑问句保留原词：
✔ I wonder where he lives.
✔ Can you tell me what he needs?
四、表语从句（Predicative Clause）
作表语出现，通常用于 be 动词之后：
✔ The truth is that she never said that.
✔ The question is whether we can finish it today.
📌 注意：不要与主语从句混淆，要看 be 动词前是否已有主语。
五、例句对比训练
✅ 简单句：
- He said something.
- I know the answer.
➤ 提升表达：
- He said that he was sorry.
- I know what you mean.
✅ 名词性从句能替代具体词语，使句子更有抽象性和信息密度。
六、语法要点提示
- That 引导的从句不要用疑问语序：
- ❌ I think that is she right.
- ✅ I think that she is right.
- Whether 和 If 的区别：
- whether 可用于介词或不定式后：
✔ It depends on whether he agrees.
✔ We discussed whether to go or not. - if 不能用于这些位置。
七、课堂应用范文片段
Many people believe that success depends not only on intelligence but also on persistence.
It is still unclear whether the new policy will be effective.
What matters most is how we respond to challenges.
🎯 上述句子中使用了三种不同形式的名词性从句，使句子内容更饱满、逻辑更明确。
八、小结
- 名词性从句是理解英语复合句结构的关键；
- 主语、宾语和表语从句需掌握不同引导词和语序规律；
- 善于使用名词性从句可以有效提升作文语言的深度与严谨性。
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