This is the very book that I am looking for.

3. 当先行词是形容词最高级时或它的前面有形容词最高级修饰时

This is the best that has been used against pollution.

4. 当先行词时序数词或它前面有一个序数词修饰时

his is the last train that will go to Zuzhou.

5. 当先行词既有人又有物时

Do you know the things and persons that they are talking about?

6. 当主句的主语是疑问词who 或which时

Which is the bike that you lost?

Who is the boy that won the gold medal?

7. 有两个定语从句，其中一个关系代词已which用，另一个宜用that

They secretly built up a small factory which produce things that could cause pollution.

8. 当先行词在主句中作表语，而关系代词也在从句中作表语时

Shanghai is no longer the city that it used to be.