引导定语从句as与which, that的用法区别
①such…as(引导定语从句)，such…that(引导结果状语从句)
“so/such…that….”引导的是结果状语从句，从句的成分是完整的，也就是说that只起连接作用。
“such… as…”引导的是定语从句，从句的成分是不完整的，也就是说as代替先行词在从句中充当成分。比如下列三句表达的是一个意思：This is such a heavy stone as no one can lift. (定语从句)
This is so heavy a stone that no one can lift it. (结果状语从句)
This is such a heavy stone that no one can lift it. (结果状语从句)
②the same…as和the same ...that 的区别
the same…as表示“与……一样(但不是同一个)”，而the same…that表示“同一个，就是那一个”的意思。
The coat you wear now is the same as I bought yesterday.你现在穿的外套跟我昨天买的一个样。
③as和which指代主句的内容时所引导的定语从句的区别
如果有“正如，象”的含义，并可以放在主句前，也可以放在后面，甚至可以插在主句中间，那么用as；而which引导的从句要放在主句后，并无“正如”的意思。
They won the game, which we hadn’t expected.
他们赢得了比赛，这是我们没有料到的。
As is well known, he is a famous film star.正如大家知道的那样，他是一位电影明星。
A lot of language learning, as has been discovered, is happening in the first year of life, so parents should talk much to their children during that period.
正如已经发现的那样，大量的语言学习是在人的生命开始的第一年进行的。所以这段时期父母亲应该多和他们的孩子说说话。
随堂练习
1.I’ve become good friends with several of the students in my school ________ I met in the English speech contest last year.
A. who B. where C. when D. which
【答案】A
【解析】句意：我已经和去年在英语演讲比赛中遇到的我校几个学生成为了好朋友。先行词是several of the students (指人)，且定语从句中缺少的是宾语，故选A。
2.John is the boy ________ legs were badly hurt in the accident.
A. that B. who C. which D. whose
【答案】D
【解析】句意：约翰就是那个在事故中腿受重伤的男孩。先行词为the boy在定语从句中作定语，故选whose。
3.The girl handed everything ________ she had picked up in the street to the police.
A. which B. whose C. that D. what
【答案】C
【解析】句意：这个女孩把她在街上捡到的一切都交给了警察。先行词为everything，在定语从句中作宾语。当先行词是everything, nothing, anything, something, much, little, none等不定代词时，引导定语从句只能用that。
4.In the end, she decided to sell the house ________ windows were almost all broken.
A. which B. of whom C. that D. whose
【答案】D
【解析】句意：最终她决定卖掉那所窗子几乎都破掉的房子。先行词为the house在定语从句中充当定语，故用whose。 whose在定语从句中既可指人也可指物。
5.This is the best book ________ I have found all this year.
A. who B. whom C. which D. that
【答案】D
【解析】句意：这是这一年来我找到的最好的一本书。先行词book被形容词的最高级修饰，且在定语从句中充当宾语，故用关系代词that。
