It’s known to all that..........改成what is known to all is that 中为什么要加is？
作者&投稿：史云 （若有异议请与网页底部的电邮联系）
It's known to all that ...这是固定句式 “众所周知... (后接一句话)”
what is known to all is that 中 what is known to all 是主语，主语后当然要有个谓语动词，所以就有is.
它和 as is known to all 是相同的意思,都是“众所周知”,而用法上面略有些不同,as is known to all 只可以用在句首或句尾,用“,”隔开.而as it is known to all不仅可以放在句首,还可以后面加“that”从句.而it is known to all 是形式主语的典型,只用于如it is known to all that our teacher is beauful.
表语从句…
你看
把（what is known to all）看做一个整体（比如A）
没有is 主系表结构不完整
that后面的从句就是A的内容"a"
句子就是 What is known to all is that "a"....
恢复一般形式就是"a" {is} known to all.
因为第一个 is 只是主语从句中的谓语，而第二个 is 才是整个句子结构的谓语，要是不加上去的话，主框架就没有谓语了。
殷勤健肾炎： 这是众所周知的
山阳区13674314557： It's known to all that.改成what is known to all is that 中为什么要加is?我说的意思是把it换成what,that后为什么要加is - ？
殷勤健肾炎：[答案] 看: It is known to all that A loves B.(主语从句) =That A loves B is known to all.(主语从句) = What is known to all is that A loves B.(主语从句加表语从句) =A loves B,which is known to all (定语从句) = As is known to all,A loves B.(插入语结构...
山阳区13674314557： It's known to all that reading - ----one's knowledge - ？
殷勤健肾炎：[选项] A. is increasing B. increases C. has increased D. increased
山阳区13674314557： it known to all还是it is known to all - ？
殷勤健肾炎： 应该是it is known to all(that) 还有其他表达:as everyone knows; as is known to all; Everybody knows ...; it is common knowledge that ...; as we (all)know;as known to all.
山阳区13674314557： it is known to all that 和as is known to all that 区别 - ？
殷勤健肾炎：[答案] 都表示“众所周知”,但是用法不同It is known to all that the earth is round.it是形式主语;that引导主语从句,是真正都主语As is known to all,the earth is round.中间有逗号,as 引导从句,the earth is round是主...
山阳区13674314557： it is known to all that后作什么语 - ？
殷勤健肾炎： it 是形式主语, that引导的是主语从句,整体代表真正的主语; 属于强调句型. (1) 陈述句的强调句型:It is/ was + 被强调部分(通常是主语、宾语或状语)+ that/ who(当强调主语且主语指人)+ 其它部分.强调句可以强调除谓语以外的一切成分....
山阳区13674314557： It's known to all that..........把it换成what,that后面为什么要加上is.各位高手谢谢了 - ？
殷勤健肾炎： 原句it是做形式主语,真正的主语是后面that引导的从句,相当与that...is known to all.it改成What之后,就是What引导的主语从句了,这时that前要加is,变成What is known to all is that...这里that引导第二个系动词is后的表语从句.
山阳区13674314557： It is known to all放句首it一定要改为as吗? - ？
殷勤健肾炎： 不一定.要看all后面接什么?如果是that引起的一个句话.那 it不能变.如:It is known to all that the earth is round. (众所周知地球是圆的.)
山阳区13674314557： 如何区别As is known to all与It is known to all?？
殷勤健肾炎： since的语气比because弱,但比as强.since和as引导的从句一般放在句子的开头.since和as的主要区别是:用as引导原因从句语气较弱,所说明原因是附带,而since表示原因暗示着是稍加分析之后才能推断出来原因. 引导原因状语从句的连...
山阳区13674314557： it known to all和as is known to all有什么区别? - ？
殷勤健肾炎： 因为填it的话就会有两个主句,前面一句,后面一句,这是不符合语法的.填As的话前面一句就是从句,就可以.单独用都没错
