5. The sun gives off light and warmth that makes it possible for plants to grow.

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　　解析：that不可以引导非限制性定语从句。

　　答案：that→which

　　6. I've read all the books which I borrowed from the library.

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　　解析：当先行词被all every no some any little等修饰时，常用that引导定语从句。

　　答案：which→that或去掉which

　　7. This is the best film which I have ever seen.

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　　解析：当先行词被序数词、形容词的最高级或the only the very等所修饰时，常用that引导定语从句。

　　答案：which→that或去掉which

　　8. My father and Mr. Smith talked about things and persons who they remembered in the country.

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　　解析：如果先行词既指人又指物时，常用that引导定语从句。

　　答案：who→that

　　9. Everything which we saw was of great interest.

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　　解析：当先行词为something anything everything nothing all等时，常由that引导定语从句。

　　答案：which→that或去掉which

　　10. His dog that was now very old became ill and died.

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　　答案：that→which

　　Ⅳ.语法填空

　　Wife: __1__ I phone and tell your secretary you're not going today?

　　Husband: Yes please dear. Tell her I've got __2__ cold and have a headache but hope to be back in a day or two. You'd better say I __3__(stay) in bed.

　　Wife: But you are not in bed. Do you want me to tell a lie?

　　Husband: Oh it's only a little __4__， dear. I'm not making a false excuse. I really have a bad headache.

　　Wife: Then put the cigarette __5__. It's very foolish __6__ you to smoke when you've got a cold.

　　Husband: Very well dear. You're quite right.

Wife: Look here's some __7__(boil) water. Do __8__ I tell you now.