由as,which 引导的非限定性定语从句,as和which可代整个主句,which相当于and this或and that.1)As一般放在句首,which在句中.2) as也可在句中往往和see,know,expect等词连用.
a.He seemed not to have grasped what I meant,which/and this greatly upsets me.
b.The sun heats the earth,which/and this is very important to us.
c.As was expected,the beautiful girl married a handsome boy.
d.As we all know,smoking is harmful to one's health.
e.He must be from Africa,as can be seen from his skin.
定语从句中若先行词前有the same,such作修饰语,通常用as作关系代词.
He used such expressions as he could find in the texts.
They stayed for the night in the same room as they had once rented.
such…as和such..that
such…as定语从句,as在从句中可以作主语,宾语,表语；such…that引导结果状语从句,that不充当任何成分,只起到连接作用,如：
They talked in such simple language as children could understand.
They talked in such simple language that children could understand it.
the same…as和the same…that
两者都可以引导定语从句,但the same…as指两件事物,而the same…that指同一件事物：
He is using the same pen as I did 10 years ago.
他用的这支钢笔和我十年前用的那支一个样.
He is using the same pen that I did 10 years ago.
他用的这支钢笔就是我十年前用的那支.