当状语, 就用关系副词. 如果充当主语或宾语则用关系代词.

I want to buy the house, which has a garden.

The school, which Mr. Cheng set up ten years ago, has changed greatly.

The story in the book takes place in Canada, where Doctor Bethune was born.

2. 关系代词的选用

1) 非限制性定语从句的关系代词不能用that. 分别用who, whom来指代主语和宾语, 指物时用which, 引导词作宾语是不能省略.

Mr Zhang, who came to see me yesterday, is an old friend of my father's.

2) 非限制性定语从句由"介词+关系代词"引导时, 关系代词不能用who, that和as, 在此结构中关系代词指人和只能用whom，指物时只能用which.

I finished my homework ahead of time, after which I sat some time watching TV.

Chaplin went to the States in 1910, by which time he had learned to dance and act in comedies.

语法延伸:

as和which均可引导非限制性定语从句, 用于指代整个句子的内容.

1) 由as引导的非限制性定语从句可位于主句的句首, 句中或句末, 而which引导的非限制性定语从句只能放在主句的后面.

A s we all know, smoking is harmful to one's health.

= Smoking is harmful to one's health, as we all know.

= Smoking, as we all know, is harmful to one's health.

He married her, which / as was natural.

2) 当从句中的谓语动词是否定形式或从句谓语动词带复合宾语时, 一般用which而不用as.

He admires everyone in the class, which I find quite strange.

3) which可以为"这件事, 这一点"; as意为"正如...., 像.....", 常用于固定搭配中, 如as is often the case这是常有的事; as is known to all众所周知; as is mentioned above正如上面所提到的.

As is known to everybody, the moon travels around the earth once every month.

4) 在"介词+关系代词"引导的非限定性定语从句中, 关系代词只能用which, 不能用as.

No. 3 Hospital, in which I was born, is a famous one in this area.

补充练习一:

1. Wind power is an ancient source of energy _____ we may return in the near future.

A. on which B. by which C. to which D. from which

2. Just use this room for the time being, and we'll offer you a large one ___ it becomes available.

A. as soon as B. unless C. as far as D. until

3. More and more high-rise buildings have been built in big cities _____ space.

A. in search of B. in place of C. for lack of D. for fear of

4. Amy joined a painting group but didn't seem to _____, so she left.

A. show off B. go up C. fit in D. come over

5. They've won their last three matches, _____ I find a bit surprising actually.

A. that B. when C. what D. which

6. _____ the website of the Fire Department in your city, and you will learn a lot