6.“the same ...as”, “such...as” 中的as 可以指人或物，作从句的主语、宾语、表语或介词的宾语。如：

Such money as he earned was spent on spirits and tobacco.

Is this the same mosquito as bit you just now?

He was not half such a coward as we took him for.

5.指人时只能用who不用 that的情况

1). 先行词为one, ones或anyone.　

2). 先行词为those.　

3). 在there be开头的句子中。

There is a man who called himself Mr. Wu at the gate.　　　

4). 在非限制性定语从句中。

4.指物只能用which 不用that的情况　

1).在非限制性定语从句中　　

2).在介词后面

3、只能that用做关系代词的情况(共9种类型)。

　 1>.当先行词是all, everything, anything, nothing, much, little, none, one等不定代词时(something除外)，只用that。

歌诀助记：不定代词这路货，全用that准没错。

　　 Pay attention to everything that I do.

　 2>.当先行词被序数词或形容词最高级修饰时，只用that。

歌诀助记：先行词前被限定，千万不要用which.

　 This is the best novel (that) have read.

3>.如果出现两个或两个以上的先行词，并同时兼指人和物时，关系代词用that。

歌诀助记：两项并列人与物，引导定从用that.

They were talking about the person and things that they remembered in school.

4>.当先行词被the only, the last, the way, the same等等修饰时。

　 This is the last time that I shall give you a lesson.

5>.在疑问词who, which, what开头的特殊疑问句中,为了避免重复只用that。

　 Which of the students that knows something about history.

6>.当定语从句为there be 句型时，关系代词只能用that,也可以省略。

This is the fastest train (that) there is to Beijing.

7>.当指人或物的关系代词在定语从句中做表语时，关系代词只能用that,也可以省略。如：

China is not the country (that) it was.

8>. 当先行词被All, every, no, some, any, little, much等修饰时，只用that。

　 He has little time that he can spare.

9>.当被修饰的成分是数词时，(被修饰成分是代名词one，指人时除外)只用that.

　 I’ve got one that you might be interested in.

2、that, who, which做主语时，从句中谓语动词的数必须和先行词一致。

He is the only one of the teachers who is respected and loved by all the students.

他是唯一一位受所有学生尊敬和爱戴的老师。(受尊敬和爱戴的只有一位老师)。

核心解读一：

1、1>关系代词的省略情况

That , which, who, whom做宾语、表语时可省略。

He isn’t the man (that) he was.

The man (man) I spoke to is my brother.

The book (that/which) I borrowed yesterday is very interesting.

关系代词在从句中做介词宾语，而介词不在关系代词前时可省略。

This is the very book (that/ which) I have been looking for.

That可做关系副词，往往省略，先行词多为 way, day, time, moment等。

I don’t like the way (that=in which) he talks.

This is the third time (that) he has been late this week.

2>关系代词的选用情况。

用于指代先行的名词或名词同等语并兼具连词功能引导从句与先行词之间关系的词叫关系代词.

如果一个句子中缺成分<常常是选空后的句子缺主语、宾语或表语等>(一个简单的英语句子至少要有主语和谓语，谓语动词若是及物动词时则必须要有宾语)，就要选择关系代词(that, which, as, who, whom, whose)。不缺成分就只能缺句子的壮语,所以就应选择关系副词(when, where, why)。

I walked in the yard，____Tom and Jim were tying a big sign onto one of the trees.

A. which　　 B. when　　 C. where　　 D. that

[点拨]：答案C。选空后的句子，主语是Tom and Jim。谓语是were tying。宾语是a big sign。句子中不缺成分，所以要选关系副词when或 where 。Tom and Jim两人的动作发生的场所是yard，所以只有选表示地点的副词C. where。

7、先行词前有So ，such， as ，same等时，用 as引导定语从句。

6、先行词是the way 或the reason时，关系词的选择。

5、用Whose或of which引导的定语从句。

4、先行词是整个句子或句子的一部分时，用as或which引导的非限制性定语从句。