❤As 引导的非限制性定语从句
Refers to a whole sentence
♡ 将整个主句作为先行词，对其进行修饰，这事从句谓语用第三人称单数：
He seems not to have grasped what I meant,which greatly upsets me.
Liquid water changes to vapor(n. 蒸汽),which is called evaporation (n. 蒸发；消失).
2.All the magazines here which have beautiful pictures in them were written by him.
里面有漂亮图画的那些杂志是他写的。
All the magazines here,which have beautiful pictures in them,were written by him.
所以杂志都是他写的，里面都有漂亮的图案。
which和as 用法的区别
✿which引导非限制性定语从句不能至于句首，而as可放在句首，中，末
✿由as构成常见搭配：as we all know,as is known to all,as is said above等
表示“正如…”，而which不能
例子：
My cousin whose father is a teacher wants to be an actor.
，whose father is a teacher，wants to be an actor.
1. This is the place where I lived 10 years ago.
The school,where I once studied,was built 30 years ago.
2. He is a man who I can ask for help.
His father,who works in Beijing,came back yesterday.
✿固定句型：
as has been said before 如上所述 as may be imagined 正如可以想象出来的那样
as is well known 众所周知 as was expected正如所预料的那样
as has been already pointed out 正如已指出的那样 as we all can see 正如我们都能看到的
例子：As is known to everybody,the moon travels around the earth once every month.
As is often the case,we have worked out the plan..(情况通常如此)
As is reported in the newspaper,talks between the two countries are making progress.作者: xiaomeixin 时间: 2011-11-28 18:34
This is very important to us who want to learn English well.作者: 小尾巴猪 时间: 2011-11-28 18:37
