“介词+关系词”的用法
1、关系代词在从句中作介词的宾语时，介词常可以提前，但介词提前时，关系代词只能用which 或whom。
如：The school (that/which) he once studied in is very famous.
→The school in which he once studied is very famous.
Tomorrow I will bring here a magazine (that/which) you asked for.
→Tomorrow I will bring here a magazine for which you asked.
We'll go to hear the famous singer (whom/that/who) we have often talked about.
→We'll go to hear the famous singer about whom we have often talked.
2、关系副词when, where, why 和介词+which之间的关系。
关系副词when, where, why可以用适当的介词+which来替代。介词的位置非常灵活，有时放在关系代词之前，有时放在动词之后。如：when=in/on/at…+which, where=in/on/at…+which, why=for+which ）
如：I won’t forget the date when( on which) I was born.
This is the room where (in which) I lived. = This is the room which I lived in.
I do n’t know the reason why (for which) he hasn’t come today.
Tom still remembers the days when (in which) they lived in Tianjin.
注意：
1). 含有介词的动词短语一般不拆开使用，如：look for, look after, take care of等
如：This is the watch which/that I am looking for. (√) This is the watch for which I am looking. (F)
2). 若介词放在关系代词前，关系代词指人时用whom，不可用who或者that；指物时用which，不能用that；关系代词是所有格时用whose
如：The man with whom you talked is my friend. (√) The man who/that you talked with is my friend. (F)
The plane in which we flew to Canada is very comfortable. (√)
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The plane in that we flew in to Canada is very comfortable. (F)
3).“介词+关系代词”前可有some, any, none, both, all, neither, most, each, few等代词或者数词
如：He loved his parents deeply, both of whom are very kind to him.
In the basket there are quite many apples, some of which have gone bad.
There are forty students in our class in all, most of whom are from big cities.
4). 把握“介词＋关系代词”结构中介词的选用
介词的选择与主句中先行词的搭配密切相关。
如：That”s the reason for which he was late for school. This is the book on which I spent 8 Yuan.
介词选择的三大规则：
1. 取决于从句中的谓语动词同介词的搭配。（V+ pre.）
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如：He is the man whom I talked with this morning.
2. 取决于先行词同介词的常规搭配。
四组常考的搭配：1）extent degree （程度）同to 搭配
2）price(具体多少钱时与at; 若指价格方面
与in 搭配) speed rate
同at搭配
3）field area aspect sphere （领域，方面）同in 搭配
例句：The field in which I studied in university is psychology.
4) basis ground foundation （基础）同on 搭配
英语四六级语法：被分隔的定语从句
定语从句一般紧接被它所修饰的先行词；但有时候它和先行词之间有可能插入其他成分，使它与先行词分隔开来，这种定语从句叫作被分隔的定语从句，在阅读文章时会经常遇到这种情况，在阅读是要注意识别先行词的修饰对象。
一般说来，定语从句被分割开来大致有以下三种：
①在先行词与定语从句之间插入一个状语。
There are many thousands of stars in the sky that are like the sun.
在太空中有成千上万的象太阳般的星星。
乍一看，that引导的定语从句在名词sky的后面，似乎应该是修饰sky的。但仔细一想，不对啊，天空怎么能象太阳呢原来that引导的定语从句被in the sky这个地点状语分隔开来，修饰中心词stars。
②在先行词与定语从句之间插入一个定语。
如：Do you remember one afternoon ten years ago when I came to your house and borrowed a diamond necklace？
你还记得吗，十年前的一天下午，我来到你家，找你借了一条钻石项链？
when I came to your house and borrowed a diamond necklace实际上是修
饰afternoon而不是修饰years。ten years ago 实际上是定语后置修饰afternoon。
③先行词与定语从句被谓语分隔开来。此时，先行词通常是句子的主语，因定语从句较长，主句谓语较短，为使句子平衡，常将定语从句移至谓语之后
如：A new master will come tomorrow who will teach you German. 明天，新（男）老师将来教你德语