名词性从句：
表语从句
1.表语从句的含义
作主句的表语
This kind of thinking is (why so many people try to avoid arguments……）
2.表语从句的写法
that 不做成分，也不能省略
Part of the issue is (that airports have only so much room for screening lanes)----that 后面的句子是个完整的句子，不缺成分，所以加 that
This is (where developing new habits comes in)
This is（ why repeated attempts at reform legislation have failed in recent years……）
3.表语从句的位置
系动词后
For Williams ,these activities become what he calls"electronic heroin"
Yet the fact remains （that the merger movement must be watched）----yet 在句首，通常指的是这个句子与上句话的关系。
Human nature being (what it is),most people stick with default settings-----只要是系动词后就是表语从句，至于这个系动词做的是句子的谓语还是非谓语，没有关系
The explanation for insensitivity to smell seems to be (that the brain finds it inefficient to keep all smell receptors working all the time but can create new receptors if necessary)------finds it中的it 是形式宾语，真正的宾语是后面的to do ；the brain是从句的主语，后面讲了两件事，因为有but ；but (the brain )can create new receptors if necessary
