__is know to everybody that Russia is the biggest country in the world.空上为什么填 It 不填 As
问题描述：
__is know to everybody that Russia is the biggest country in the world.
空上为什么填 It 不填 As
答
it is known that ....意为“据大家所知”
as is known可以理解为“正如大家所知道的那样”
从意思上可以作出区分
答
It is know to everybody-------句子已经完整
that
Russia is the biggest country in the world.------句子完整
that引导的同位语从句 指代it形式主语。
As is know to everybody ， Russia is the biggest country in the world
在这里 as是介词,有 正如.... 的意思。
答
it在此只是个形式主语,真正的主语是 that Russia is the biggest country in the world
as则没有代词的功能