定语从句中只能用that的情况

只能用that 的情况：

1. 先行词为不定代词all, much, everything, nothing, none, the one

2. 先行词被only, any, few, little, no ,just, very, one of 修饰

3. 先行词被序数词或就是序数词时

4. 先行词是最高级

5. 先行词既是人又是物

6. 先行词是次数时two, ten, a hundred

7. 两从句一个已用which ，另一个用that,避免重复

8. 疑问词是who/which,宜用that

9. 主句there be

10. 被修饰部分为表语or 关系代词本身是定从的表语时：主+be+n./adj. ; 主+系+adj.

只能用which 的情况：

1. 介词后

2. 非限制性定从

3. 当关系词后带插入语时

只能用who 的情况:

1. 先行词为anyone, anybody, those, all, one, ones, they, he, people

2. 非限制性定从

3. There be

先行词为way 时，定从常用that, in which, how, that. that 可省

As 的用法：

正如……As 是关系代词，代替整个句子，在后面的句子中充当动词know 的宾语。 He was a foreigner, as I know from his accent.

如为限制定从，多用于the same…as, such…as…, as many/much as, so as

I have the same book as you (have).

Her attitude to him was quite the same as it had always been.

I live in the same house that he used to live in. I’m wearing the same shirt as you were yesterday.

非限制定从中，as 常至于句首。

As we all know, smoking is harmful to one’s health.

as 做主语

as is well known (to us)

as was mentioned before

as could be expected

as could be judged from her eyes

as may be seen from the book

as is recounted in his stories

as everyone could do

as often happens

as will be shown in fig.3

as has been pointed out

as has been explained

as is often the case

as (is) usual

He listed the names as follows (follows永远是单数)

as做宾语

as we all can see

as we all know

as it is

成分不重复

关系词省略：

1.非正式文体中

2.关系代词做宾语，常略

3.以the way为先的限制性定从常由in which/that引导，常略

4.The time when, the place where, the reason why中，when, where, why可略

不能用that的情况：

1.非限制定从

2.关系词前有介词