一个关于主语从句谓语动词为被动是否用先行it结构的问题~语法高人来指导~

1. It is known to us all that the earth moves around the sun.
=That the earth moves around the sun is known to us all
that 引导主语从句放在句首时,主句的谓语可以是被动语态,如上两句表达都对,只是更习惯用
it is known that.
2.wh-或whether引导主语从句的例子如下：两句表达都对
When the wedding will be held hasn't been decided
=It hasn't been decided when the wedding will be held
Whether he will go to the wedding isn't known to us
=It isn't known to us whether he will go to the wedding.