___is known to us all is that the earth is smaller than the sun.why not use "what".why not use "it"
问题描述：
___is known to us all is that the earth is smaller than the sun.
why not use "what".why not use "it"
答
what
答
What注意：is that the earth is smaller than the sun这是系表结构,缺主语,所以用What如果用 it 那that the earth is smaller than the sun 就是真正主语,可是它前面有 is应该这样才对_It__is known to us all that...