关系分句&关系词的选择
在复合句中起了形容词的作用，在句中修饰一个名词或代词的从句叫做关系分句（定语从句），被修饰的词叫做先行词（antececdent)，引导定语从句的词叫关系词，他的作用一是放在先行词与关系分句中间起了连接作用，二是在分句中担当一个成分，并与先行词保持数的一致。
关系分句分为限制性关系分句和非限制性关系分句。
关系词分为关系代词（that, who, whom, which, whose)、关系副词（when, where, when, why)和关系限定词（whose）.
具体关系词的选择如下:
考虑三个因素（限定性、指人还是指物、充当的成分） 一般：who/whom/that指人 which/that指物
1．that
that在定语从句中可以指人也可以指物，
在从句中作主语或宾语，但不能放在介词后作介词宾语。如： The eggs that I bought yesterday were not fresh. 我昨天买的鸡蛋不新鲜。
I prefer dumplings that have just been cooked. 我更喜欢吃刚煮出来的饺子。
指物时that和which可以互换，但下面几种情况通常用that引导定语从句，不能用which。
（l）当先行词有最高级修饰或本身就是最高级时。如： This book is the most difficult one that I have ever read. 这本书是我所读过的最难的一本书。 The best that I could do was to apologize. 我能做的最好的事情就是道歉。
（2）当先行词有序数词修饰或本身就是序数词时。如： Here are two students，the third that you want is to come in a minute.这儿有两个学生，你要的第三个学生一会儿就来。 The second school that I visited here was Yucai Middle School. 我在这儿所参观的第二所学校是育才中学。 （3）当先行词是all、不定代词如（something，anything, nothing，little, much，none）时。如：
在限制性关系分句中关系词的选择
There is little that I can do to make up for the lost time. 我没有办法弥补所丢失的时间。
All that is worth doing is worth doing well.值得做的就值得做好。 （4）当先行词前有only，all，any，no等词修饰时。如： There are no people that things must not happen to. 没有人一生不出事。
The only thing that they could do was to sleep. 他们所能做的事就是睡觉。
（5）当先行词在svc结构中作表语（主语补语）时,而且还通常省略。如：
This is the school (that) I once studied at. 这就是我曾经上学的学校。
当先行词在there be（存在句）结构中做“实义主语”时，而且还通常省略。
The 9:15 is the fastest train (that) there has ever been. （7）当先行词既含有人又含有物时。如：
They talked about the persons and things that they remembered in the school.他们谈论还能记起的在学校里的人和事。
The man and manners that he describes in his book are familiar. 他书中所描述的人以及所用的手法都很熟悉。
（8）句中有两个定语从句，其中第一个从句的关系代词已用了who或which时，第二个定语从句的关系代词用that。如： Our English teacher is the man who is talking with the girl that is in red.我们的英语老师就是那位男子，他在和穿红衣服的女孩谈话。 We built a factory which produces fertilizer that is badly needed. 我们修建了一个工厂，生产急需的化肥。 （9）在以who开头的疑问句中。如： Who is the boy that is standing at the gate？ 门口站的那个男孩是谁？
Who was she that he danced with? 和他跳舞的那个女士是谁？
2.which
which在定语从句中指物，作主语，动词宾语或介词宾语。如：
The building which stands near the river is our school. 河边的那所建筑物是我们学校。
This is the reference book which you want.
这就是你要的那本参考书。
下面几种情况通常用which，不用that: （l）关系代词在介词后面时。如： This is the chair on which I sat just now. 这就是我刚才坐的那把椅子。
That is the house in which we lived last year. 那就是去年我们住的房子。
如果要用that引导定语从句，则介词不能放在前面，只能放在从句中相关动词的后面。在含有介词的固定短语动词中，介词不能提前。
（2）在非限定性定语从句中。如：
They are hollow, which makes them very light.． 它们是空的，这使得它们很轻。
The book,which was written in 1994, was published in 1996. 1994年写的那本书，1996年才出版。 （3）先行词为that时。如：
What's that which you are looking at? 你们正在看什么？
What's that which you are holding in your hands?你手里拿的什么？
关系代词whom, which在定语从句中作介词宾语时，介词一般放在whom,which之前。关系词的选择：
正式语体：介词前置，whom指人，which指物
It is a tribute in which the British-speaking peoples can share irrespective of party or class.
James Russell is a man for whom I have the greatest respect. 非正式语体，介词后置，who/that指人，that指物，或者都用zero. There are the boys (who/that) I went to school with. The case (that) you are referring to is now closed.
关系代词whom, which在定语从句中作介词宾语时，介词一般放在whom,which之前。介词由两方面来确定。 （l）根据动词和介词的搭配来确定。如： This is the house in which we lived last year． 这就是我们去年住的房子。
There comes the man about whom we just talked. 我们刚才谈论的那个人过来了。 （2）根据从句的意思来确定。如：