定语从句之专题二：that引导定语从句（系统讲解内在原理）

3.that 不但可以代替关系代词(who(m)/which)，也可以代替关系副词(when/where/why)。

①一般地，关系代词who(m)/which可以被that代替或省略。

例句（关系代词被that代替，或者省略。）

●He is the man (whom/that/∅) I saw yesterday. 他就是我昨天见的那个人。

●The package (which/that/∅) you are carrying is about to come unwrapped.你拿的包快散了。

②当先行词为the time/place/reason等明确表示时间/地点/原因的词时，关系副词when/where/why可以被that代替或省略。（这是因为，此时的代替或省略，不会产生歧义。）

例句（关系副词被that代替，或者省略。）

●I’ll never forget the day when/that/∅ we met.我永远也忘不了我们见面的那天。

●That is the place where/that/∅ we went before.那就是我们以前去过的地方。

●That’s the reason why/that/∅ I took it.那就是我买它的原因。

4.用that代替who(m)/which，可以防止引导词重复。

何谓“重复”？不是单词的重复，而是词头的重复。（that的词头是th-，与who(m)/which的词头是wh-。）

①前句用了“th-”，后句再用“th-”，叫重复；所以，如果前句用了“th-”，后句就不宜用“th-”，而用who(m)/which。②前句用了“wh-”，后句再用“wh-”，也叫重复。所以，如果前句用了“wh-”，后句就不宜用“wh-”，而用that。（一般地，这条规则是软规则，不是硬规则。也就是说，尽量不要重复，但是即使重复了也不算错。）

例句（如果前有疑问词who(m)/which/what等，引导词宜用that。）

●Who is the person that supports your family?

●Which is the bus that you will take?

●They secretly built up a small factory, which produced things that could cause pollution.

例句（如果先行词是that/those时，引导词宜用who(m)/which。）

●People all like those who(常用)/that(不常用) have good manners.

●What’s that which flashed in the sky just now?