定语从句中‘介词+which’的用法

介词+WHICH在定语从句中可以代替when,where,和why,用哪一个介词要看先行词和从句谓语动词,介词要能够与先行词搭配使用
、"介词+关系代词"引导的定语从句
关系代词whom,which在定语从句中作介词的宾语时,可以跟介词一起放在主句和从句之间;当先行词指人时,介词后的关系代词用whom,其余用which,这时的关系代词不能省略;有时为了使关系代词紧跟它所修饰的先行词,也可以把介词放在从句中有关动词的后面,这时的which可用that替换.当介词放在从句有关动词的后面时,关系代词which,that,whom在口语中和非正式文体中经常省略.如:
This is the room in which he used to live.= This is the room (which / that) he used to live in.这是他过去居住过的房间.
Who's the man with whom you just shook hands?=Who's the man (that / whom) you just shook hands with?刚才你与他握手的那个人是谁?
但含有介词的短语动词一般不拆开,介词仍放在动词的后面.如:
This is the book (which / that) I'm looking for.这就是我在找的那本书.
在这类定语从句中,介词的选择一般根据动词的需要,如上述几例,或者根据先行词来决定.如:
There is a mountain of which the top is always covered with snow.有一座山顶总是覆盖着雪的山.