that引导的主语从句:
1. It is + adj. (obvious, true, natural, surprising, wonderful, funny, possible, certain, ect.) + that 从句
It is certain that she will do well in her exam.
that 是否可以省略?
That she will do well in her exam is certain.
( )
that 在句首时绝对不能省. 口语中that引导真正的主语时,that可省.