1．who,whom和whose引导的定语从句
(1)who或whom均可指代人， 但who在从句中作主语或宾语， whom在从句中作宾语； 两者在引导限制性定语从句时可用that替换。 作主语时， who/that不可省略； 作宾语时， whom/who/that可以省略。
◆I’ve become good friends with several of the students in my school who/whom/that I met in the English speech contest last year.
我与好几位去年在
英语演讲比赛中结识的同校同学成了好朋友。
◆I have many friends to whom I’m going to send post cards. 我有很多打算寄贺卡给他们的朋友。
◆The person I want to talk about with you is Tu Youyou, the one who won the Nobel Prize in Physiology or Medicine in 2015.
我想与你讨论的人是屠呦呦，2015年获得诺贝尔生理学或医学奖的人。
(2)whose表所属关系， 一般指人，也可指物， 在从句中作定语。 指物时相当于of which; 指人时相当于of whom。
◆The school shop, whose customers are mainly students, is closed for the holidays.
这家校内商店的主要顾客是学生， 放假时商店关门。
关系代词在定语从句中作主语时，从句谓语动词的人称和数要和先行词保持一致。
◆Tom is the only one of the engineers who has come up with the solution.
汤姆是想出解决方法的唯一工程师。
2．that,which引导的定语从句
(1)which指物， 在从句中可以作主语、宾语，也可作定语，作宾语时可以省略。that指人或物均可， 在从句中可以作主语、宾语、表语， 作宾语时可以省略。
◆She showed the visitors around the museum that/which had been constructed three years before.
她带着这些游客参观了那座三年前建造的博物馆。
(2)限制性定语从句中， 关系代词只用that不用which的情况：
①先行词为不定代词anything, nothing, something, everything, all, some, none, little, few, the one等时。
◆I refuse to accept the blame for something that was someone else’s fault.
我拒绝接受因别人的错误而对我进行的指责。
②先行词是形容词最高级或序数词， 或先行词前有形容词最高级或序数词修饰时。
◆The first place that they visited in Guilin was Elephant Trunk Hill.
他们在桂林参观的第一个地方是象鼻山。
③先行词被the only, the very, the last, the same, any, every, each, few, little, no, some，all等修饰时。
◆The only part of the meal that I really liked was the dessert. 这顿饭只有甜点是我真正爱吃的。
④先行词中既有表示人又有表示物的名词时。
◆They will never forget the things and persons that they’ve seen or heard of during their long journey.
他们将永远不会忘记在他们的长途旅行中见到或听说过的人和事。
(3)关系词只用which而不用that的情况：
①关系词引导非限制性定语从句时。
◆The boy was away from home for a week, which worried his parents very much.
这个男孩离家一个星期了，这使他父母很担心。
②当从句中的介词提前， 构成“介词＋关系代词” 结构时。
◆We live in an age in which more information is available with greater ease than ever before.
我们生活在一个信息比以前更容易获得的时代。
3．as引导的定语从句
(1)as可以引导限制性定语从句，常用于“so/such/the same＋先行词＋as…”结构中。
◆Such machines as are used in our workshop are made in China. 像在我们车间使用的这种机器是中国制造的。
which引导定语从句代指前面整句话内容时只能位于主句之后。
◆(安徽高考)Mo Yan was awarded the Nobel Prize for Literature in 2012, which made one of the Chinese people’s long held dreams come true.
莫言被授予2012年诺贝尔文学奖，这使中国人长久以来拥有的梦想之一变成现实。
(2)as也可以引导非限制性定语从句， 定语从句说明整个句子， 可放在主句之前、之中或之后。常用的这种类似插入语的句式有：as the saying goes, as is said above, as is mentioned above, as often happens, as is often the case, as is reported in the newspaper等。
◆She has been absent for the meeting again, as is expected. 她又缺席会议了，这在预料之中。
[典例] (2015·全国卷Ⅰ语法填空)I’d skipped nearby Guilin, a dream place for tourists seeking the limestone mountain tops and dark waters of the Li River____________are pictured by artists in so many Chinese paintings.
that/which 解析： 先行词为waters，且引导词在从句中作主语，故填that/which。
单句语法填空
1．(2015·陕西高考)A salesman ____________ is not punctual may not make a sale if he arrives late for an appointment.
2．(全国卷Ⅰ)Maybe you have a habit ____________is driving your family crazy.
3．(2017·福建龙岩质检)Tibet is such a place____________ all the people across the world are dreaming of visiting.
4．(2016·江苏高考单项填空)Many young people, most of ____________ were well educated, headed for remote regions to chase their dreams.
5．(2015·四川高考单项填空)The books on the desk，____________ covers are shiny，are prizes for us.
