3、介词词组(关系代词远离先行词)

In front of, on top of ,at the foot of, with the help of, as a result of.

We stand in a building in front of which stands a lab.

We arrived at a hill, on top of which stood a tower.

2、非固定词组，介词位置灵活，关系代词使用严格。

The man (whom/ who/ that) I spoke to is a friend of mine.

The man to whom I spoke is a friend of mine.

1、固定词组，介词置于后，关系代词使用灵活。

This is the child (whom / who/ that) she is looking after.

3、关系代词在从句中作介词的宾语，而这个介词又在句末时。

This is the artist (whom) I spoke to you about.

注意：关系代词的省略是指在限制性定语从句中，在非限制性定语从句中，关系代词不能省略。

2、关系代词在从句中作表语时。

Mary is no longer the girl (that) she used to be.

1、关系代在从句中作宾语时。

Have you received the book (that) I sent you last week?

5、which 用作表语，指人时，一般指从事某种职业或是有某种特性、品质或才能的人。

He is an engineer, which I am not。

关系代as：在限制性定语从句中用在such, the same, as, so之后，as引导的定语从句常采用省略形式。

I have the same book as you(have).　　　　　　　　　　　 Take as many as you want.

Here is so big a stone as no man can lift.　　　　　　　　　　 This is such a book as was given to me.

4、先行词后有插入语时，

Here is the English grammar book which, as I’ve told you, will help improve your English.

3、先行词本身是that时：What’s that which flashed in the sky just now?

2、先行词在从句中作介词的宾语且介词前置。

This is the house in which Lu Xun lived.