表语从句中分别是什么时候用that,what,who,when,where,which,why,

that仅起连接作用，无意义，在句中不作任何成分，通常不可省略。这种从句往往是对主句主语的内容起进一步解释的作用。
连接副词when,where,how,why除在句中起连接作用外，在从句中还充当时间、地点、方式、原因状语，本身具有词义。
which可以作表语从句么？？？！

关系代词的应用区别于状语和定语从句
要区别以上代词
需要从最基本的分析句子成分开始
单独举一大堆例子也没多大作用

表语从句中分别是什么时候用that,what,who,when,where,which,why,
是根据句子的意思而定的
He has become a teacher.
He has become what he wanted to be ten years ago.
She has remained there for an hour.
She has remained where I stood yesterday for an hour.
His suggestion is good.
His suggestion is that we should stay calm.
The question is confusing.
The question is when he can arrive at the hotel.
who will travel with me to Beijing tomorrow.
why he cried yesterday.
how I can persuade her to join us in the party.
whether the enemy is marching towards us