介詞 which 定語從句
1、語法作用：
“介詞＋關係代詞”在從句中主要起關係副詞的作用，即在定語從句中充當狀語：
（1）表示地點，時間和原因的“介詞＋which”分別相當於where，when，why。
I have found the book in which the names of all the early satellites are mentioned.（SEFC 2A L. 55）（＝I have found the book. The names of all the early satellites are mentioned in it.）
The earth on which／where we live is a planet.
I”ll never forget the day on which／when I joined the League.
I know a wood in which／where you can find roses.
Is there any reason for which／why you should have a holiday？
（2）way後常用that代替in which，也可省略that。
I really don”t like the way that he talks.
That was the way in which the old lady looked after us.
Do it the way I showed you.
2、“of＋which”起形容詞的作用，相當於whose（用來指物），其詞序通常是“n.＋of which”。
They live in a house whose door／the door of which opens to the south.
He”s written a book whose name／the name of which I”ve com- pletely forgotten.
3、可引導限制性定語從句和非限制性定語從句
There is a rocket by which the direction of the satellite can be changed.（SEFC 2A L. 55）
We carefully studied the photos，in which we could see signs of plant disease.（SEFC 2A L. 55）
4、介詞的選擇（選擇介詞時須考慮下列情況）
（1）介詞與先行詞的習慣搭配
There is no way in which it could be brought back to the earth.（SEFC 2A L. 55）（in與way是習慣搭配）
（2）介詞與定語從句中的動詞，形容詞的習慣搭配
These are the wires with which different machines are connected.（be connected with是習慣搭配）
The author with whom all of us are familiar will visit our compa-ny.（be familiar with是習慣搭配）
（3）同形的先行詞，或定語從句中的動詞，形容詞表示不同的.含義時，要根據其含義選用不同的介詞。
I can”t remember the age at which he won the prize.
That is the age in which people live in peace and happiness.
age在前句中意為“年歲”，與at搭配；在後句中意為“時期”，與in搭配。
（4）複雜介詞須保持其完整形式，常見的複雜介詞有on the top of，in the middle of，in front of，in spite of，at the back of，because of等。
We took a photo of rocket，the length of which was about 30me- tres.（SEFC 2A L. 55）
Sound is a tool by means of which people communicate with each other.
They marched through the square，in the middle of which stood a monument.
（5）短語動詞中的介詞不可與動詞分開提至關係代詞前。常見的短語動詞有listen to，look at，depend on，pay attention to，take care of，look into，break into，get rid of，take part in，make use of，take hold of，catch hold of，catch up with，get along with，look forward to等。此時可用which，who，whom或that，也可將他們省略。
（誤）This is the girl of whom he will take care.
（正）This is the girl whom he will take careof.
（6）當介詞與定語從句中的動詞或形容詞聯繫緊密（但不是短語動詞）時，介詞也可放在動詞或形容詞的後面。但當介詞與從句中的動詞或形容詞聯繫不緊密時，則需將介詞置於關係代詞前。比較：
The space station which we drove to was in the desert.（SEFC 2A L. 55）
I”ll never forget the day in which I joined the Party.
後句中的in若置於句尾則有“孤零零”之感，這時宜將介詞置於關係代詞前；而前句中的to則可後置。
5、關係代詞的選擇
用於介詞後的關係代詞只有which，whom，前者指物，後者指人。
There are many research stations on the earth in which outer space is studied.（SEFC 2A L. 55）（which指代research stations）
We questioned the pilot，from whom we learnt that no other planes had been seen.（SEFC 2A L. 55）（whom指代the pilot）
