8.Have you found the book for which I paid $10?

　9.Have you found the book on which I spent $10?

　10.Have you found the book about which she often talks?

　11.Air, without which man can't live, is really important.

　13.This is the river, along which we often have a walk.

（2）Conclusion:介词+关系代词+定语从句中介词的选定

A、根据定语从句中先行词的搭配习惯确定；

B、根据定语从句中谓语动词的搭配习惯确定；

C、根据定语从句所表达的意义来确定。

考虑三个因素: "一先,二动,三意义"

（3）Fill in the blanks with proper prepositions:

1. The sun gives us heat and light, ______ which we can't live.

2. The student ______ whom we were talking just now is the best student in our class.

3. I'll never forget the day _____ which she said good-bye to me.

4. This is the tree ______which we used to play games.

Step 4.有些动词短语中的介词与动词是固定搭配，不可以拆开，此时介词不能前置：

This is the watch for which I am looking. (F)

This is the watch which/that I am looking for. (T)

The boy of whom she takes care is 7 years old. (F)

The boy (who/whom/that) she takes care of is 7 years old. (T)

Step 5.介词前置时，whom/which不能省略，但如果介词位于句末时，whom/which可以省略。

This is the house in which / where he used to live.

The man to whom you talked just now is a famous singer.

Use a preposition and a relative pronoun, whom/which, to complete the following sentences.

1. The book ___________ I heard was written twenty years ago.

2. The people ________ the man spoke weren't listening.

The film ____________ I fell asleep was very boring.