求助关于✀which✀的用法

1、在后置的非限制性定语从句中代替上文出现的事物或者情况（单数或复数）.
2、在问句中作疑问代词,在名词从句中作为连接代词用,其含义为“哪儿,哪些”.
3、如果非限制性定语从句的先行词不是指主句内容,而是指具体的人、时间、地点,则不用which.
这里主要讲解一下再定语从句中的用法：
一、关系代词that和which在定语从句中作主语和宾语,放在先行词和定语从句之间,起联系作用,指物时,一般情况下可互换,如：
Here is the pen that/which you lost yesterday(that/which 指物作宾语)
A plane is machine that/which can fly（that/which指物,做主语）
He is the most careful boy that I know（that指人,作宾语）
The man that works in this room is a chemist（that 指人,作主语）
二、that、which在从句中作主语时,不能省略.作宾语时在口语中和非正式问题中经常省略.如上例1和3中的that、which都可省略.
三、关系代词在主语从句中作主语时,从句的谓语动词的人称和数须贺先行词一致.
wheat is a plant that/which is grown in the north of China.
四、在定语从句中,关系代词that和which指物时,一般没有区别,但下列几种情况中不能互换：
1、只能用that的情况：
a、先行词为all、everything、nothing、anything、little等不定代词（something后也可以用which）：
Is there anything （that） I can do for you town?
That is all （that） I Know.
b、先行词被序数词所修饰时：
The first thing （that） we should do is to work out a plan.
c、先行词被形容词最高级所修饰时：
This is one of the most exciting football games（that）I have ever seen.
The nanjing yangtse river bridge is the longest bridge (that) they ever seen.
d、先行词被形容词最高级修饰时：
This is the only thing （that） we can do now.
He gave me the same pen (that) were written by Lu Xun?
This is the very books that were
e、当先行词中即有人又有物时：
The man and the car （that）you want to see are all here .你想见的人和车斗在这.
f、that 可指人,which则不能.
who is the man that is reading new paper over there?
g、 在“the time when”等结构和某些事件状语中,when常被that代替,而且that往往被省略.
I may leave here any time I want to.
During the time I was there I visited him twice.
h、 way 后面可根由that引导的定语从句,但that一般都省略：
That was the way she looked after us.
在下列情况下,只能用which
a、放在介词后面做介词定语时：
This is the question about which we’ve had so much discussion
但是,如果把介词放在从句后部.这时which 就可换为that并常省略,如上例可以改为：
This is the question that we are had so much discussion about.
b、在非限定性定语从句,无论指物指人,都不能用that,指物时,只能用which和其他关系代词,如：
All the books there,which have beautiful pictures in them,were written by him.
这个地方注意一下：引导词和先行词
引导词：就是引导从句的词,比如whether,how,what ,why,when等具有引导其后从句功能呢过得词.
先行词：定语从句的引导词前面的被定语从句所修饰的名词、代词.在定语从句中充当一定的成分.