----- is well known to everybody is that Nanning ,Wuhan,Chan

_____ is well known to everybody is that Nanning ,Wuhan,Changsha and Chongqing are extremly hot in summer.A.It B.as C.that D.what 答案选what,as is known to everybody,it is known to everybody that,what is known to everybody is that 不是都适用吗,为什么只能选what

如果用it ,句子里面就会出现两个谓语.as 和 what 可以领导从句,it 不可以,所以不用.你在看这一个句子,到everybody 前是一个从句,而从句前面并没有先行词,不是定语从句,是主语从句.as 只能引导非限定性定语从句,所以用what