定语从句中当先行词是物时，什么时候用that ？什么时候用which

that和which都指事物时，一般可以通用。但在下列情况下必须用that，而不能用which:

1先行词为all，everything, nothing, something, anything, much little, few, none, the one等时。例如：

Say all(that)you know.把你知道的全部讲出来。

Is there anything(that)I can do for you now?现在需要我为你做点什么吗?

This book contains much little that is useful.这本书中有很多(没有多少)有用的东西。

I mean the one that was bought yesterday.我指的是昨天买的那个。

2先行词为数词或被序数词(含last)修饰时。例如：

This is the first film(that)I have seen since I came here.这是我到这里以来所看的第一部电影。

The last place they visited was the Summer Palace.他们最后参观的地方是颐和园。

Look at those presents. You can see the two that you gave me.看那些礼物，你能看见你送我的那两个吗?

3先行词被形容词的最高级或the very, the only等所修饰时。例如：

This is the biggest apple(that)I have ever eaten.这是我所吃到的苹果中最大的一个。

She is the very thief(that)the policeman is looking for.她就是警察正在寻找的那个小偷。

Mary is the only friend(that)I have in Australia.玛丽是我在澳大利亚唯一的朋友。

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