结构中的主语从句不可提前。 什么意思啊

It is said/reported/suggested/…+that Clause(从句)
在这类句型中,由于后面真正的主语从句较长，为了避免整个句子头重脚轻，就要用it作为形式主语，放在句首，而真正的主语从句放在后面。

错误：
That he is a burglar is reported.（从句义上来说没有错，但是根据英语的语法结构不能这样写）

正确：
It is reported that he is a burglar.

it是形式主语，后面的从句才是真正的主语，故称为主语从句。
如It is said that he was born in a poor family.但我们不能说
that he was born in a poor family it is said.