每课一句：新概念英语第1册第121课
【往期回顾】
接下来，我们就来看看第121课的“每课一句”。
一、课文原文
Lesson 121 The man in a hat
I bought two expensive dictionaries here half an hour ago, but I forgot to take them with me.
Who served you, sir?
The lady who is standing behind the counter.
Which books did you buy?
The books which are on the counter.
Did you serve this gentleman half an hour ago, Caroline? He says he’s the man who bought these books.
I can’t remember, sir. The man whom I served was wearing a hat.
Have you got a hat, sir?
Yes, I have.
Would you put it on, please?
All right.
Is this the man that you served, Caroline?
Yes. I recognize him now.
——选自《新概念英语》第一册，外语教学与研究出版社，1997年10月第1版
二、每课一句
The lady who is standing behind the counter.
本课开始学习定语从句的用法，本课侧重的是关系代词的显性用法，即不省略时的用法。
（一）两个概念
1、先行词
定语从句所所修饰的名词或代词或其短语。
2、关系词
用来连接定语从句的关系代词或关系副词。本课侧重的是关系代词的用法。
如：
The man whom I served was wearing a hat.
其中，
the man是先行词
whom是关系代词
whom I served是定语从句
（二）关系代词
常见的关系代词有：who, whom, whose, which, that。其中：
从句缺主语时，用who/which/that。
从句缺宾语时，用who/whom/which/that。
从句缺定语时，用whose。
1、who
当who用作关系代词时，其先行词表人，且在定语从句中作主语或宾语。如：
作主语：He is the man who helped me yesterday.
作宾语：He is the man who I helped yesterday.
2、whom
当whom用作关系代词时，其先行词表人，且在定语从句中作宾语。如：
She is the girl whom I spoke to just now.
She is the girl to whom I spoke just now.
3、whose
当whose用作关系代词时，其先行词既可表人也可表物，且在定语从句中作定语。如：
Do you know the woman whose daughter is a pilot?
Do you like the room whose window faces south?
4、which
当which用作关系代词时，其先行词表物，且在定语从句中作主语或宾语。如：
作主语：The pen which cost me two hundred yuan is on the shelf.
作宾语：The pen which I bought there yesterday is very expensive.
5、that
当that用作关系代词时，其先行词既可表人也可表物，且在定语从句中作主语或宾语。如：
作主语：The teacher that will teach us English next term is from Italy.
作宾语：The book that you lent me yesterday is very interesting.
三、更多拓展
Is this the man that you served, Caroline?
虽然关系代词that的先行词既可以是人也可以是物，但有的时候无论其先行词是人还是物，都必须使用that：
1、先行词中含有不定代词；
2、先行词中含有序数词；
3、先行词中含有最高级；
4、先行词中含有the only/very/same等词时；
5、先行词中同时含有人和物时；
6、主句是以who或which引导的疑问句时。如：Who is the man that you served you just now?
7、先行词是主句的表语或关系代词在定语从句中作表语时。如：China is no longer the country that it used to be。
【注意】
以上情况并且穷尽所有必须使用that的情况；此外，也有的情况是不能使用that的，比如当关系代词紧跟介词时，就不能使用that。
