求教介词+which的用法

1、表示地点，时间和原因的“介词＋which”分别相当于where，when，why。

The earth on which／where we live is a planet．

I'll never forget the day on which／when I joined the League．

2、way后常用that代替in which，也可省略that。

That was the way in which the old lady looked after us．

3、“of＋which”起形容词的作用，相当于whose（用来指物），其词序通常是“n．＋of which”。

They live in a house whose door／the door of which opens to the south．

介词的选用原则：

1、根据定语从句中谓语动词的习惯搭配

This is the book on which I spent $ 8.

This is the book for which I paid $ 8.

2、根据先行词的搭配习惯

I remember the days during which I lived there.

I remember the day on which I graduated from university.

3、根据整个句子所表达的意思来决定

The colorless gas without which we can’t live is called oxygen.

4、英语中为了强调某一名词，不定式前面也可以加上关系代词。

Here is the money with which to buy the piano.

She is the right person on whom to depend

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。

用作定语的从句叫做定语从句(attributive clause)。定语从句通常皆置于它所修饰的名词(或代词)之后，这种名词(或代词)叫做先行词(antecedent)。引导宾语从句的关联词为关系代词和关系副词。关系代词在定语从句中可用作主语、宾语、定语等;关系副词在定语从句中只用作状语。如：
The student who answered the question was John. 回答问题的那个学生是约翰。(who answered the question是关系代词who引导的定语从句，用以修饰who先行词student，who在从句中用作主语)
I know the reason why he was so angry. 我知道他这么生气的原由。(why he was so angry是关系副词引导的定语从句，用以修饰why的先行词reason，why在从句中用作原因状语)
定语从句一般紧跟其先行词之后。

介词＋which 的确是个难题，许多语法书上都只是简单地描述一下。建议不要想把这个问题一下子全都解决。下面我给你说这个问题的第一个要点：介词从哪儿来？为什么要加介词？介词第一个来源是先行词，依据先行词来确定用什么介词。如： The hotel at which they are staying is very expensive. 这个at就是根据hotel来定的，在酒店at the hotel。再如：The lab in which he is working is well equipped. 这个in 就是根据先行词lab ，在实验室in the lab 。

介词+which 可以用介词+it来代替，只是it 不能引从句，所以用which。
我也是自学的英语，但我只关心一个词怎么用、什么意思，理论的东西一向不太关心。而且我发现中文的语法书写得太复杂，明明很简单很好理解的东西，看完语法书的解释后反而糊涂了。所以建议你多听多读，见得多自然知道怎么用