who的用法四种句型：可以用作疑问代词，也可以用作限制性或非限制性的关系代词。
1.谁， 什么人 Who is that woman in the red hat?那个戴红色帽子的女人是谁？I wonder who will play in the basketball match.我不知道这场篮球赛谁会上场。
2.（限制性关系代词）…人 He who laughs last laughs best.最后笑的人笑得最开心。
All who[that] heard him were delighted.所有听了他讲话的人都很高兴。
He is the only one who[that] knows Russian.他是我们中间惟一懂俄语的人。
3.（非限制性关系代词）他， 她， 他们 The committee, who were all young women, fulfilled their duties admirably.委员会的委员们都是些年轻妇女， 很好地履行了她们的职责。
关系代词who引导定语从句作句子的主语、宾语。定语从句由关系代词who、whom、whose、which、what、as和关系副词where、when、why等引导。
who的用法
1.who引导的定语从句的先行词是表示人的名词或代词。例如：
（1）The student who is answering the question is John.
正在回答问题的那个学生是约翰。
（2）Anybody who breaks the laws will be punished.
任何违反法律的人都将受到惩罚。
2.who是主格，在定语从句中作主语，此时不能省略。例如：
（1）The person who was here yesterday is a musician.
昨天来这儿的那个人是位音乐家。
在非正式英语中，who亦可作宾语，且可以省略。例如：
（2）The man（who）I saw just now is Mr Li.我刚才见到的那个人是李先生。
3.在定语从句中，who在人称、数上和其前面的先行词保持一致。如：
Do you know the boy who is standing over there?
你认识站在那边的那个男孩吗？
4.若先行词中既有人又有物，关系代词用that而不用who。例如：
He watched the children and boxes that filled the car.
他看见了塞满汽车的孩子和箱子。
5.若先行词前面有形容词最高级、序数词修饰，关系代词用that而不用who。例如：
（1）Yao Ming is the best basketball player that I know.
姚明是我知道的最好的篮球运动员。
（2）Tom is the first boy that left the room.
汤姆是第一个离开这个房间的男孩。
who[英][hu:][美][hu]
pron.谁; 什么人; 关系代词，有先行词; 孰;
一、强调句型的用法
在英语中，我们常用It is／was… who/that结构来突出强调句子的某一成分(一般是句子中主语，宾语或状语)。在这个句型中，it没有词汇意义，只是引出被强调的成分。如果被强调的成分是表示人的词，用who或that来连接都可以。如果是其它成分，则一律用that来连接。
E.g. It is my mother who／that cooks every day.
E.g. It was yesterday that Tom passed in the maths exam．
二、使用本句型的几个注意事项
1．被强调成分是主语，who／that之后的谓语动词应该在人称和数上与原句中的主语保持一致。
e.g. It is I who am right． e.g. It is he who is wrong．
e.g. It is the students who are lovely．
2．即使被强调成分是句子中的时间状语，地点状语，原因状语等，也不能用when，where, because，要用 that。
E.g. It was after the war was over that Einstein was able to come back to his research work again .
E.g. It was in front of the bank that the old lady was robbed．
E.g. It was because of the heavy rain that he came late．
3．如果被强调的成分有同位语，同位语也应提前。
It was from him，his chemistry teacher，that Paul learned to watch carefully in class．
4．被强调成分是作主语的代词，用主格，是作宾语的代词，用宾格。 It was he that helped me yesterday. It was me that he helped yesterday.
5．被强调部分既包括人又包括物，用that不用who
lt was the things and people that they remembered that they were talking about．
三、考试中，为了增加试题难度，强调句型经常以疑问句形式出现。其一般疑问句形式是：
Is／Was it+被强调成分+who／that
Is it Mr.Smith who teaches you English?
其特殊疑问句形式是：疑问词+is／was+被强调成分+that...
Why was it that you did not attend the meeting yesterday?
When was it that this traffic accident happen?
Where was it that you put my English dictionary?
四、区分定语从句和强调句型某些定语从句和强调句型形式差不多，容易混淆。如果去掉it is／ was ... that句子仍然通顺成立，则为强调句型，不成立不通顺，则为定语从句。
E.g. It was three years ago that he went to American for a further study·
去掉It was that句子为Three years ago he went to America for a further study．句子通顺，意思完整，那么，这就是一个强调句型。
it is...that/who...用作强调句时，不作句子成分，也就是说去掉it is that 句子还是能够单独使用。这是和定语从句的区别。还用that引导的名词性从句也是这样的。 下面讲下强调句型：
1. 强调句型特点是：去掉It be …that/who…，句子成分完整。
It is in the street that I met her 强调句 把it is that 去掉，句子完整，in the street I met her. It is clear that not all boy like foot ball，去掉后，clear not all boy like football不完整，不是强调句（是主语从句）
2. 强调句中只有that/who/whom,不会出现where，which, when等。
It is the street where I met her 定语从句 where 关系副词 做定语从句中的地点状语；
3. 如果强调时间地点 就看前面有没有介词, It is in the morning/at some place that.......一般情况下就是强调
判断是否是强调句一般用以下方法：
把 It is/was ……that 去掉，看句子是否完整，若完整，则为强调句，若不完整，则为从句。 例：It was at the school gate that I met an old friend of mine.(强调句)
It was the school gate where I met an old friend of mine. （定语从句）
