主语从句是用从句充当主语的句子结构，常见的类型包括：名词性从句、强调句型和疑问句型。以下是具体分类：
| 类型 | 特点 | 例句 |
| 名词性从句 | 由that、whether、if等引导 | That he passed the exam surprised us. |
| 强调句型 | 用It is...that...结构 | It is she who helped me. |
| 疑问句型 | 由疑问词引导，如who、what、how等 | What he said made no sense. |
这些类型在语法中各有用途，掌握它们有助于更准确地表达复杂意思。
