关于介词+which/whom引导的定语从句,介词的选择的具体用法,一定要有例子分析,

介词+which 相当与 where , 表示在哪里的意思， 而介词+whom 就表示···某人
那么这两个都是用在定语从句中， 介词的选择是根据定语从句中的谓语动词所接的介词，也就是这个动词常见的搭配介词来绝对
如： the place at which i have just arrived is very beautiful. 在这里，at 的选择是根据后面的arrive 来决定 的， 因为arrive at 后接一个小地方，用介词at ,所以选择at.

j介词的选择要看定语从句中谓语动词与先行词的搭配而定
例如：The person ___ I spoke just now is my sister. 填 to whom 因为定语从句中的谓 语动词和先行词the person 构成的惯用搭配为：speak to the person
This is the farm —— I once worked . 填 on which(=where）因为定语从句中的谓语动词work 与先行词the farm 构成的惯用搭配为work on the farm.
有时需要分析句子的意思再定介词：
如：Mandela was generous with his time,for which I was very grateful.
这里介词用for 因为be gtateful (to sb) for sth. 因为某事感激某人用介词for，此处which指代主句全句。
Einstein is a person，for whom moemey is not important.
此处介词用for是对于他来说，钱并不重要。即for him money is not important

介词选择要根据从句的动词来定
eg:I don't know the person with whom you talked just now.我不认识刚才和你讲话的人.此处从句为 talk with sb.和某人交谈.用talk with
I don't know the person about whom you talked just now.我不认识你刚才谈论到的那个人.此句中为talk about sb.谈论某人.用talk about
当先行词是物的时候用which是,也是考虑从句动词与先行词的搭配
eg.could you find the bus by which you get here.
could you find the bus in/on which you saw the fight.