名词性从句包括：主语从句、表语从句、同位语从句、宾语从句。
★ that 的省略问题：
在引导主语从句、表语从句、同位语从句时that都不能省略，引导宾语从句时that能省略。
一、主语从句 Subject Clause
(1)主句单复数问题
如：What we need is more money.
What we need are more experienced teachers.
(2)形式主语 Form Subject it
1.It is+adj.Ved/noun+that 结构
如：That the earth is round is true/a fact.
It is true/a fact that the earth is round.
2.It+Link V+that 结构 seem，appear, follow, turn out，come out
如：It seems that you know a lot about computer.
It happened that I was not there that day.碰巧，恰好
He drives a BMW.It follows that he is rich.因此
二、表语从句 Predicative Clause
Reason 的用法：
如：The reason why/that he is late is that he met an accident.
Reason 作主语的表语从句后面连接词只能用 that.
练习：
The reason _________ I’m writing is to tell you about my examination results.
A. because B. as C. why D. for
三、宾语从句 Object Clause
(1)介宾
1.that 常只作如下介词宾语
in that 表原因，意为“在于”
如：Men differ from brutes in that they can speak and think.