宾语从句that不可省的情况

Question

在看别人说明用法的时候，有个句子不能理解。“当主语从句有it做其先行词时”能否举个例子解释说明下这句话？

Answer 1

that引导的宾语从句，一般可以省略that，但在以下6中情况中that不可以省略：
1.在由and和but连接的两个并列的宾语从句中，第一个从句中的that可以省略，第二个从句中的that不能省略。如：I know (that) you are very kind and that you can help me.
2.当that宾语从句中的状语位于从句的前部时，that不可以省略。如：Tell him that if he comes tomorrow, please call me.
3.当that前面有插入语时，that不可以省略。如：He didn't know, I'm sure, that his mother was ill.
4.当it作为形式宾语放在动词之后，而that引导的真正宾语从句放在句尾时，that不可以省略。如：They took it for granted that the singer was coming.
5.在省略答语中，当that宾语从句单独出现时，that不可以省略。如：
----What did you say?
----That he would be here at 8 o'clock.
6.当that宾语从句是双宾语中的直接宾语时，that一般不省略。如：I swear. I will never tell anyone that you have broken the glass.

Answer 2

这是主语从句：为了防止句子头重脚轻，通常把形式主语it放在句首位置，真正主语搁置于句末
（1）It is certain that he will win the match.

（2）It is true that he has made a very important discovery in
chemistry.

（3）It is very likely that they will hold a meeting.
（4）It is strange that he should do that.本回答被网友采纳

Answer 3

that 要做成分.是不能省.it is said that stl is very handsome.