in which 的用法

1. in which是介词加关系代词，引导定语从句
in可以放到从句中去
our immune system breaks down in this condition

2. 把in放进从句中应该是这样的：

it is transmitted from one person to another in the way.

不是都能组成动词短语的，你得了解介词加关系代词引导定语从句时，介词如何去选择，不光是由从句动词去决定，还可能是由先行词决定，等等。

（1）以从句中动词；形容词；名词与介词的固定搭配而定；
[高考考例]2. In the dark street, there wasn’t a single person _____ she could turn for help. [MET 1992]
A. that B. who C. from whom D. to whom
[思路点拨]答案为D. turn to sb for help 为固定搭配表示“求助于某人”
（2）以先行词与从句中的动词关系及所表达的含义而定或以先行词在定语从句中的作用与含义而定。
[考例]1. The medicine of science, ______ progress has been very rapid lately, is perhaps the most important of all the science.
A. to which B. in which C. which D. with which
[思路点拨]答案为B.从句主谓结构搭配为：progress has been rapid in, 这里的in意为“在某方面”，相当于rapid progress has been made in the science of medicine.
[考例]2. The professor made his first speech _____ he talked about some subjects the students were interested.
A. that B. which C. in which D. of which
[小结]关键词：介词的选用与从句主谓结构的搭配有关。

in which 用于定语从句，作关系副词，在句中不做成分。in which=where
in which 只能用在定语从句中，等于where,在定语从句中作状语
如果先行词(指定语从句修饰的那个表地点的词)前已有前置词(介词)，关系副词就用where ；如果先行词前没有前置词，此时既可以用where，也可以用in which,但在美国的TOEFL考试中一般要用in which。例如：①The offices,laboratory,and museum are situated at te top of the hill whe re they command a fine view.(参考译文：办公室、实验室和博物馆都坐落在山顶上，从那儿他们可以俯瞰周围秀丽的景色。)句中用where是因为top前已有前置词at。②The farmer uses wood to build a house in which to store grains.(译文：农民用木头造了一间房子，用来储存粮食。)
详见：http://wenku.baidu.com/link?url=kMyId3loy-8MXd21Gl0zm5O4eD16uiUBMmwNP7vZNvMegoLI40Bv1E0EKwil--OkbLzVzCD9xT9Z0H4nraKirnaISb657XS41PV8XYGPkgS

which用于定语从句，作关系代词，在句中要做成分
inwhich用于定语从句，作关系副词，在句中不做成分，inwhich=where
inwhich只能用在定语从句中，等于where,在定语从句中作状语。
如：HelivedinthehouseinwhichTomoncelived.
HelivedinthehousewhereTomoncelived.
定语从句中.如
thisistheroominwhichwestayed
先行词是room，后的句子是用来修饰room的
但是room不可做stay的成分，因为stay是不及物动词，后不可直接家宾语
所以要有个介词．
其实上述的句子＝
thisistheroomwhichwestayedin．
这里的介词是可以提到which前的
注意，第二个句子可用that或省略
但第一个只能用which．只有which前可加介词

in which room did you come yesterday?
这里用了in 是因为宾语是room ,你把它翻译成陈序句，应该用in this room 吧。 就是这样得
of which bottles some are empty?
那些瓶子中是混杂着有空的得？
你也写为陈序句，就是some of this bottles are empty
所以就是用of

同学,这里的in wich 引导定语从句，而且in 不和从句动词组成词组，而是和先行词组成词组．
第一句组成in the condition
第二句组成in the way