by which怎么用…Some others consider all the diplomas as importa

其实就是一般的限定性定语从句
至于前面的介词取决于主句中的动词
比如this is the pen by which i wrote compisition
不能呆板于介词＋which是何用法

y which=by the amount（以...的量),翻译是:赤字是某物比要求的或预期的量少的量,特别是总收入比总支出少的量

2. The average length of labor during which these women received their meperidine was under 12 hours.
4. Socially Awkward Situations During Which It Would Be Acceptable to Mess With Texas.
5. Fish evolve a longer lifespan by evolving a longer period during which they reproduce.
4. Have been fostering for five years, during which time they have fostered 20 children.
5. ... registry will occur on 9/24/2006 from 9 PM to 9:45 PM EDT, during which time you will be unable to register, renew or manage .
这些都是google上搜到的原版英文句子,可以看出一个规律,during which的中心语大部分是表示时间段的名字例如period等；而duiring which time的中心语常常是具体的时间如5 years等.
具体的原理我不记得了,希望这样的对比能对你有所启发.

which 是引导定语从句的关系代词,指代定语从句所修饰的名词（先行词）.具体which 前面是什么介词,只要将定语从句还原,使其语序正常后,就容易找出.如
The bike ___ which I went to school was stolen.
还原后的定语从句是:I go to school___ the bike.显然介词是on.by bike 是固定搭配,这时候的bike 前不用冠词,是抽象的用法,所以不能选by.
针对楼上的回答.

不等的.
by which (by的意思由具体语境而定)可理解成,借助于.通过.,等,用于定语从句中,也可用在特殊疑问句中.如：
He bought a new bike by which he can reach his factory in less time.

在句中by which是指通过输出/输出数据集来确定输入向量的过程 by是通过的意思,通过这个过程
on which 是指在这个过程中模糊推理模型并没有建立,而是在建立之前.
on是在的意思 在这个过程中.不可以用by

y which they mean 结构 为什么用by,
理由：这里是mean...by 结构
比如：What do you mean by "success"?你说success是什么意思?
What do you mean by doing that?

which用在定于从句里后面跟的介词是根据从句里的动词来决定的
动词搭配的介词就是which 后该用的介词
I choose the house in which I can play Pingpang
I like the table to which I can see the outside
I take the means by which I can get the goal
I get the paper on which she leave the message
I choose the romm of which door is high enough

Take the key,by which you can open the door.
把这把钥匙拿去开门吧.

给你几个例句看下（来源google)
2.The average length of labor during which these women received their meperidine was under 12 hours.
4.Socially Awkward Situations During Which It Would Be Acceptable to Mess With Texas.
5.Fish evolve a longer lifespan by evolving a longer period during which they reproduce.
4.Have been fostering for five years,during which time they have fostered 20 children.
5....registry will occur on 9/24/2006 from 9 PM to 9:45 PM EDT,during which time you will be unable to register,renew or manage .
这些都是google上搜到的原版英文句子,可以看出一个规律,during which的中心语大部分是表示时间段的名字例如period等；而duiring which time的中心语常常是具体的时间如5 years等.
具体的原理我不记得了,希望这样的对比能对你有所启发.

介词 on 是 travelling on the train
用 by which的话
把 定冠词 the 去掉
但是 这句句子主干是 the train was late(此处the 不可省略)
所以 用by which是不合适的

这是定语从句,thermal power station （热电站）是先行词,which是引导词,后面的从句原来的句序是the environment will be polluted by thermal power station ,by 提前,就变成了by which,by也可以不提前.另外的例子有 I am waiting for the bus by which I go to school everyday.

一般情况下
on which= when
for which=why
in which=where

C
in 为从句中 修饰Chinese astronauts 和 which指代的manned spaceship 之间关系的必要介词
Chinese astronauts 不能 at,也不能 by ,更不能 from --manned spaceship
所以C

will be arriving是将来进行时.
will have arrived是将来完成时.
首先,这句话的意思是说6点的时候所有宾客都来了,所以晚饭要在6点准备好.这是将来的时间点要用将来时.
其次,根据句中by,可以知道是在某个时间点之前已经发生了某个动作,应该用完成时.根据句意,也应该是6点,宾客已经到了,而不是正在到达,所以用will have arrived

在定语从句中,当先行词是way,定从中不缺主、宾,关系词用that、in which或省略.

前提是在定语从句中,关键要讨论先行词是时间还是地点.但是有些引导词是不能替换的：例如：by which,from which----因为这些介词本身就有意义了,就不能像when、where这样只替代先行词的意义了.
能替代的,可以互换的往往是前几个常见的：例如--at which = when、where

这里“by which” 明显是“介词+关系代词”引导的定语从句.

by which在从句中充当状语,表方式.which指代的是the reactions,而不是指“Enzymes”
即: synthetic organic substance are degraded in the body by the reactions.
句子大意：
酶被 (持怀疑态度的) 认为有助于甚至引起（生化）反应；通过这些（生化）反应,合成有机物质在体内而分解.

注意：
酶（enzymes）是催化特定化学反应的蛋白质、RNA或其复合体.
也就是说,酶是生物催化剂,主要是起催化作用（改变化学反应速率的作用）,这点你应该也知道.

因此上面的句子指的是,合成有机物质在体内是通过（生化）反应而分解,其中酶只是起催化作用（可能是有助于甚至引起这些生化反应）.

另外：从英语句子结构来看,定语从句的关系词是要尽可能紧跟在先词后面的,以免产生歧义.

看来还得高手出马
－－
定语从句的解题关键是清楚先行词要在从句做一个成份,然而学会还原定语从句就OK了.
我们来看例子中那个先行词在定语从句做什么,还原如下：
a compnay can generate revenue to sustain itself By A Method
(a method..为which所替代,而which相当于一个名词,只能做主语宾语表语,在这里是做by 的宾语； 或者which和by一起构成从句的方式状语.)
由于by 和which的关系密切,为表达更紧密起见,by前移至which前方保持正常语序
－－－
我们再来看另一个例子
This is the place in which I used to spend most of my free time.和上题一样
Thi is the place where I used to spend most of my free time.(in the place 为where 所指代,where 可以做状语,相当于in which)

主要是看后面状语的搭配 比如,i live in guangdong,in which(=where) crops grow here.这里后面的意思应该是,crops grow in guangdong ,所以用in（地点） i caught the bus ,on which i met my teacher.这里后面的意思应该是i met my teacher on the bus,所以用on（地点） i like ,by which i improve my english 这里应该是 i improve my english by reading english.所以用by（方式） i like skiing,from which i can get a lot of happiness.这里是 i can get a lot of happiness from skiing.所以用from 做这种题,你先看看后面那个从句里要搭配什么样的介词,做熟了就容易了.

你确定正确答案不是A.where?
你答案看错了吧?
如果答案真的是B,那你的原句a place后就少了个介词in
which,in which,on which,for which,by which——你说的这些全部都是在定语从句中出现的吧?这些介词并不是和which形成固定搭配,而是和which前的先行词搭配的
就说这句（如果你句子抄错了的话）A shopping center is a place in ____many different shops and stores are collected under one roof.
这里的which实际上就是指place这个词,在从句中为了避免重复而用了which引导下面的从句,也就是place的修饰语部分.
如果你没有抄错句子的话,这句话应该选A.where=in which（也即in the place）
再拿这个题问一下你的老师.你的老师可能忙中有错.我们静等他的解释.