(1) The school (that/which) he once studied in is very famous.
= The school in which he once studied is very famous.
(2) Tomorrow I will bring here a magazine (that/which) you asked for.
= Tomorrow I will bring here a magazine for which you asked.
(3) I have a dresser in my bedroom, which there are many cosmetics on.
= I have a dresser in my bedroom on which there are many cosmetics.
(4)The dumpling House which he often has dumplings at is very popular.
= The dumpling House is very popular, at which he often has dumplings.
The plane may be several hours late, in which case there’s no point in our waiting.
（固定搭配：in the case)
The speaker paused to examine his notes, at which point a loud crash was heard.
（固定搭配：at the point)
Ten years of hard work changed her greatly, for which reason he could hardly recognize her at first sight.（固定搭配：for the reason）
The film at which I fell asleep was very boring.
（Here "at which" is based on "fell asleep at the film"因为电影无聊而睡觉。）
The little creature in which scientists are interested is known as ET.
（这里"be interested in"是词组原因）
This is the book for which he is looking.
（即等于This is the book which he is looking for，这主要是因为look for 这一短语）
例题：1. I can’t believe that the restaurant, ______ I have eaten such wonderful meal, is going to be close down.
A. where B. at which C. about which
【解答】选B。这个是非限制性定语从句，at which在功能上等于where，但就本题而言只能选at which。因为at which I have eaten such wonderful meal是一个插入语，where固然可以引导，但是由于前面有了一个逗号，就只能用at which了。“我难以相信我曾经在里面美美地吃过几顿大餐的饭店就要关张了。”非限制性定语从句主要就是先行词+逗号“，”+介词+which或者是先行词+逗号“，”+which，它和限定性定语从句的最显著区别一个是有逗号，一个是非限制定语从句总有which。
2. Wind power is an ancient source of energy ______ we may return in near future.
A. on which B. by which C. to which D. from which
【解答】选C。return to其实，应该来说，就是一个固定搭配了，解释为回归到，但是呢，如果要说意思的话，也是说得通的，就是把句子换一换语序你就可以看出来了。“we may return to wind power in near future.”也就是说，看到prep.+ which这种形式，就可以直接把它扔到动词后面，然后在进行选择，看缺少哪个介词。
3. We have gathered nearly 100,000 quilts, _____up to half have gone to flood-hit areas.
A. with which B. in which C. for which D. of which
【解答】选D。这里的which指的是，nearly 100,000 quilts（被褥），也就是说，后半句的主语是在这nearly 100,000 quilts里面的up to half。
例：I don’t know the reason why/for which he did it.
The reason why/for which he was fired was not clear.
There are many countries in Asia, of which China is the largest one.
附：whose和 of which的区别
1. 关系代词whose，引导定语从句时，既可指人，又可指物，在从句中只能作定语；of whom只能指人；of which只能指物，有时whose可以与of whom和of which互换使用。如：
The girl whose hair is golden is from England. 头发金色的那个女孩是英国人。
The house whose doors(of which the doors) are green is an office building. 门是绿色的那座房子是办公楼。
2. “介词 + whose +名词”引导定语从句。如：
I love my motherland, for whose good future I will work hard. 我爱我的祖国，为了她美好的未来我要努力工作。
3. 在下列情况下，一般只用of whom和of which。
(1) 定语从句的主语是few, little, some, most, many, much等时，一般只用of whom和of which。
In the room are lots of people, many of whom I don’t know. 房间里有很多人，很多人我不认识。
He has a lot of story-books, a few of which I have never read. 他有很多故事书，有几本故事书我还从未看过。
(2) 定语从句的主语是数词、形容词的最高级时，一般只用of whom和of which。如：
The old man has three children, two of whom are college students and one of whom is a manager. 那个老人有三个小孩，其中两个是大学生，另一个是经理。
(3) 定语从句的主语是all, none, both, neither, each等不定代词时，一般只用of whom和of which。如：
There are fifty students in our class, all of whom are working hard. 我们班有五十个学生，所有这五十个学生学习都刻苦。
He planted two trees last year, both of which are growing well. 去年他栽了两棵树，这两棵树都长得好。
(4) 在定语从句中作表语的定语时，一般只用of whom和of which。如：
He has three brothers, of whom Li Lei is the youngest one. 它有三兄弟，李雷是他们中最小的一个。
There are many countries in Asia, of which China is the largest one. 亚洲有很多国家，中国是最大的一个。
The house windows face south is our reading-room.
A. of which B. whose C. which D. its
【解答】此题正确答案是B，不能选择A。选择of which时应在名词前加上定冠词the，也就是名词前有the就只能用of which。如果名词前没有冠词，就用whose。若上题改为The house the windows face south is our reading-room，则此题只能选A不能选B了。
(6) of which除了可以表示所属关系外，还可以用来表示整体的关系，而whose则不能。例：
He borrowed a book of which the author was a peasant.
In Barcelona the Chinese team got 16 gold medals, of which 12 were won by women.
第一句中的of which就可以用whose来代替，因为这个句子中of是用来表示所属关系的。可改写成：He borrowed a book whose author was a peasant. 而第二句中的of which不能用whose代替，因为这个句子中的of不是表示所属关系，而是表示整体与部分的关系。
There is a mysterious lake at the foot of the hill, whose depth has never been measured. 山脚下有个神秘的湖，其深度从未被测量过。
There are 102 elements found in nature, of which most are metals.
The story about Long March, of which this is one example, are well written.
I’d like a car whose front lights are big and round.
I’d like a car, the front lights of which are big and round.
The book, the cover of which is broken, is not mine.
The book, whose cover is broken, is not mine.