It's necessary这是什么形式?

It's necessary这是什么形式? it necessary it necessary for是不是it's necessary for的简单形式,请问它原来的结构是什么?我记得这好像是个简单形式 i think it's necessary to be friendly to others 的necessary用什么形式 it's necessary是什么意思 necessary的名词形式是什么? It's necessary for me ()my homework用finish的适当形式填空 用所给词的适当形式填空：It’s necessary ______(make) more friends. It's not necessary to the same.这句改错 I find it necessary to know more about other countriesit necessary 不应该是it's necessary. It's necessary to learn English well. 翻译it's not necessary to hurry It's not necessary _________________(相同的) it's necessary to know different (customs) of sending gifts in different countriescustom在这句话中的意思是什么,为什么加s it作形式主语和作形式宾语的区别如：I find it necessary to take exercise every day.I find it's necessary to take exercise every day.I find that is necessary to take exercise every day.这三句语法对吗?it作形式主语和作形式 it's necessary for you to give up smoking(保持句子原意) it's necessary ____you____smoke 先行词和形式主语的区别（it)It is quite clear that the whole project is doomed to failure.It's a pity that you should have to leave.这两句话It 做先行词.It is necessary that…或It is a fact that… 中的It 是做形式主语,请 early 是什么副词It is certainly necessary! it's not necessary to be the same.该句句型是：it为形式主语,真正的主语是你的句子是：