首先,你没分清先行词和引导词
例如：This is the book which I am looking for.中的book是先行词,which是引导词.
He is Mr. Robertson who comes from England. 中的Mr. Robertson.是先行词,who是引导词.
关系代词：主 格 who which that 宾 格 whom that that de的用法
通常有：on which=when
in which=where
for which=why
介词+关系代词引导的定语从句用法需注意以下几点：
1.熟及一些介词短语；例如在关系代词在定语从句中作介词的宾语时,介词可放在关系代词之前或从句之后.例如which可用that代替,whom可溶问候或that代替.例如：
Is this the dictionary (for which) you paid for five dollars?可改写为
Is this the dictionary (that/which) you paid for five dollars (for)?
此为介词短语 pay ...for...在定语从句的用法,并且在第二句中that或which可省略.
2.关系代词that在定语从句中做宾语时,介词只能放在从句结尾的相关动词后,不可放在that前面,且that可省略.
The house （that）we live （in) is large.
The house we (live) in is large.
The house in which we live is large.
The house which we live in is large.
3.介词的选用要根据从句中动词、形容词等于介词冬的习惯搭配而定.即把关系代词所代表的先行词放在从句谓语动词之后,在看动词与先行词用什么介词合适.例如：
The man to whom I spoke just now in my uncle.
4.在代词/名词+of+关系代词等从句中,先行词指人用whom指物用which.
Here are players from Japan,some of whom are our friends.