3. 主语从句不可位于句首的五种情况：

(1)if 引导的主语从句不可居于复合句句首。

(2)It is said /reported„结构中的主语从句不可提前。例如：

正确表达：It is said that President Jiang will visit our school next week.

错误表达：That President Jiang will visit our school next week is said.

(3)It happens/occurs„结构中的主语从句不可提前。例如：

正确表达：It occurred to him that he failed in the examination.

错误表达：That he failed in the examination occurred to him.

(4)It doesn’t matter how/whether „结构中的主语从句不可提前。例如：

正确表达：It doesn’t matter whether he is wrong or not.

错误表达：Whether he is wrong or not doesn’t matter.

(5)含主语从句的复合句是疑问句时，主语从句不可提前。例如：

正确表达：Is it likely that it will rain in the evening?

错误表达：Is that will rain in the evening likely?

4. what 与that 在引导主语从句时的区别

what 引导主语从句时在句时在从句中充当句子成分，如主语.宾语.表语，而that 则不然。例如： a) What you said yesterday is right.

b) That she is still alive is a consolation.

练习题：高中重点语法主语从句提升练习及答案 

英语语法主语从句的全部内容就分享完毕，愿大家在学习语法过后都能努力学习，丰富自己，锻炼自己。

相关链接

高中英语表语从句语法讲解 

高中英语宾语从句语法解析