介词搭配引导词来引导定语从句它出现的情况

定语从句由关系代词who、whom、whose、which、what、as和关系副词where、when、why等引导，但须记住：1.what不能引导定语从句。　　2.关系词的分析须考虑它在定语从句中的成分。
注：A. 介词如果位于作为其宾语的关系代词之前时，只能用whom、 which不能用who或that.
（1）The girl about whom they were talking is our monitor.
（2）The book in which there are many interesting things was written by Li Ming.
B. 部分短语动词中的介词不可与动词拆开，在定语从句中其介词不可前置，只能放在其动词之后。
Is this the book which she is looking for？The old man who/whom they are waiting for is Professor Li.The child who/whom she is looking after is Wang Ping’s son.. 关系代词放在介词之后This is the factory in which we once worked.
限制性定语从句与非限制性定语从句的区别：
从句是先行词不可缺少的定语（如去掉，主句意思就不完整或不正确。） 从句是对先行词的附加说明（如去掉，主句意思仍清楚，不受影响。） 与主句关系密切，不用逗号 与主句关系不十分密切，用逗号与主句隔开译为汉语时，从句译在先行词前，与先行词用“的”连接 译为汉语时，从句放在主句后面关系代词that可以代替who、whom（指人）、which（指物） 关系代词不用that，只用who、whom（指人）、which（指物） 关系代词代替宾语时可以省略 关系代词不能省略关系代词as和which
先研究下面两个例句：
○1.This elephant is like a snake， as /which everybody can see. =As everybody can see， this elephant is like a snake. 任何人都看得出来，这头象像条蛇。
○2.Tom didn’t pass the physics exam， which made his parents very angry. Tom物理考试不及格，这使得他父亲很生气。
这两个例句中，as和which所代表的都是整个主句所表示的内容。但有两点不同之处：
1. 在形式上as引导的非限制性定语从句可位于主句的后面，也可位于主句的前面；而which引导的非限制性定语从句只能位于主句的后面，不能位于主句的前面。　　“One of the +复数名词”后面定语从句中谓语单复数情况 　　这一结构后面的定语从句的谓语动词通常用复数形式，跟定语从句所*近的那个复数名词在数上保持一致。如：　　1. That is one of the books that are required for study at school.　　2. This is one of the most wonderful novels that have been published since 1990.3. She is one of the few persons who know Spanish .
4. This is one of the most famous plays that were written in the thirties，
如果one of +复数名词这一结构前面带有the only、the very之类的限定语，后面定语从句的谓语动词则要用单数形式，这是因为定语从句在意义上修饰的是而不是那个复数名词。如：
1.He is the only one of the teachers who knows French in our school.（ 修饰the only one）　He is one of the teachers who know French in our school.（ 修饰the teachers）　2.This is the only one of the rooms that is free now. （修饰the only one）　This is one of the rooms that are free now. （修饰rooms）