1.由that引导的主语从句

that引导主语从句时，可以置于主语的位置，但是很多时候被形式主语it代替，而将整个that从句置于句尾，这种情况下，that有时可以省略。

That most of these are now threatened and may disappear is a serious matter to the people in Britain．(人教大纲版高二上第36页)

它们大多数属于濒危语言，有可能消失，这对英国人来说是个严重问题。

That he was chosen made us very excited．

他被选上了使得我们很激动。

That he refused the offer was unlikely．

他拒绝了这个提议是不可能的。

It is likely(that)they will win the game．(人教大纲版高二下第6页)

看样子他们要赢得这场比赛了。

It is likely that people have celebrated harvest festivals ever since they began to plant and gather food．(人教大纲版高一下第80页)

人们可能从开始种庄稼和收获时就有庆祝丰收的节日了。

It is well known that Africa had contacts with India and the Red Sea civilizations from the earliest times．(人教大纲版高三第12页)

众所周知，非洲从早些时候开始就已经同印度和红海文明有过接触。