He isn't such a man ____he used to be.

A who B whom C that D as

答案是D给的解释有的说是定语从句as 作表语，有的说是状语从句as表示行为的方式。

我糊涂了，我觉得应该是定语从句。为什么that 不行呢？谢谢

回答如下：

（1）先行词被such修饰，后面由关系代词as 引导定语从句，

He isn't such a man as he used to be .( as在定语从句作表语）

中文意思：他现在不是他过去/以前的那个人了

中文意思：他现在和以前是完全不同的2个人.

中文意思：他现在和以前完全不同了.

（1）关于关系代词as代词引导定语从句详细用法

As 引导定语从句主要有2种情况：

(1)种是限制性定语从句，且先行词有as,so, such, the same或者等词修饰，它在定语从句中作主语或宾语表语的。

(2)种是先行词是代替整个主句内容的非限制性定语从句(其先行词是整个主句)

(1) 当先行词有 as, so, such, the same 修饰时，引导定语从句的关系代词用as

Such people as have made great contributions to the world should be greatly respected.

那些对世界做出巨大贡献的人应受到极大的尊重。（as作从句的主语）

You may take as many chairs as you need.

你需要多少椅子就拿走多少椅子。（as作need的宾语）

My parents have not so much money as I want.

我父母没有我需要的那么多钱。（as作want的宾语）

He made the same mistake as you made in the last exam.

在上次考试中，他犯了跟你相同的一个错误。（as作made的宾语）

Tom is not such an intelligent person as you think.

I want the same shirt as my friend bought yesterday .

Such people as have made great contributions to the world should be greatly respected.

(特别备注（1）：such.....that ...引导结果状语从句，在从句不作任何成分，such ...as 中as 引导定语从句, as 为关系代词在定语从句作主语，宾语成分.

【特别注意】

【1】在so/such...that...引导的结果状语从句中，that不作任何成分，只起引导作用。要注意区别这两种不同的结构。

They had such a fierce dog that no one dared to go near their house.他们家有一条凶狗，没人敢靠近他们家。（that引导结果状语从句，在句中不作成分）

【2】the same后有时用that，它表示“同一个，就是那一个”的意思，即同类同物；而as则表示“与……一样”，但不是同一个，即同类异物

This is the same cell phone that I lost yesterday.

这就是我昨天丢的那部手机。

This is the same cell phone as I lost yesterday.

这是与我昨天丢的相同的一部手机。

They had such a fierce dog (that) no one dare to go near their house.（结果状语从句）

He is not such a person as you think .（定语从句）

They had such a fierce dog as I had never seen.（定语从句）

This is the same book that I lost yesterday .(同类同物)

这就是我昨天丢失的那一本书.

This is the same book as I lost yesterday (同类异物)

这与我昨天丢失的那本书一样.

I bought the same dictionary as you borrowed.（同一类的2本字典）

I met the same person that I saw yesterday.(同一个人）

We have found such materials as are used in their factory（定语从句）

These houses are sold at such a low price as people expected（定语从句）

He is not the same man as he was （定语从句）

【3】但是在抽象名词，同类事物没有绝对区别，因此as/that可以换用）

I have the same opinion as /that you have.

（2） 关于as引导非限制性定语从句详细用法

引导先行词是整个主句内容的非限制性定语从句.

As 可引导的先行词是整个主句内容的非限制性定语从句,在句中作主语,宾语.它引导的从句可以位于主句前,也可以位于主句后,还可以位于主从句中间

A.位于主句之后

Tom is a brave boy, as is described in the report.

汤姆是一个勇敢的男孩，这正如在报道中描述的那样。

（从句在主句之后，as作从句的主语）

He is a great hero, as is described in the report.

正如报道中描述的那样,他是个伟大英雄.

She is a famous film star, as we all know.

正如我们都知道的,她是一个著名电影明星.

She is very patient , as is shown in her work.

She has been absent again, as is expected

B.位于主句之前(从句在主句之前，as作从句的宾语）

As everybody knows, Shakespeare was a great English writer.

众所周知，莎士比亚是伟大的英国作家。

As we had expected, the plan worked out very well.

正如我们预料的,这个计划运行的非常好.

As everybody knows, Shakespeare is a famous writer.

正如每个人/大家都知道，莎士比亚是一个著名作家.

As is known to everybody, the moon travels around the earth once every month.

=The moon travels around the earth once every month , as is known to everybody.

C.位于主句与从句之间(从句在主句中间，as作从句的宾语）

She , as we all know, can speak three foreign languages.

正如我们都知道的那样,她会说3门外语.

 The project, as we had expected, got along well.

正如我们所预料的那样，工程进展顺利。

D.as 代替前面主句整句话内容，通常用于以下【几种固定表达结构】

as引导非限制性定语从句时，常见的【固定表达】

(1) as anybody can see 正如人人都能看见的那样

(2) As is well known=as is known to all 众所周知

(3) As we (have) expected 正如我们所预料的

(4) As is often the case 正如往常那样/这是常有的事情

(5) As has been said before 正如前面所说的

(6) As is mentioned above 正如上面提到的

(7) As I remember 正如我所记得的那样

(8) as we all know众所周知   

(9) as I can remember正如我所记得的

(10) as often happens像经常发生的那样

(11) as we expect正如我们预料的那样

(12) as you see这一点你明白

(13) as was expected正如预料的那样

(14) as can be seen看得出来

(15)  as may be imagined正如可以想象的那样

(16) as has been said above 如上所述

(17)  as we all can see 正如我们都能看到的那样

(18) as is often the case 像常规那样 

(19) as everybody can do 正如人人都能做到的那样

（3）as与 which引导非限制性定语从句的区别

（1）as 引导的从句表示说话人的态度，看法，解释或者评论

( as 引导非限制性定语从句常作行为动词see, know, hear, watch, remember, say, tell, show, expect, guess的宾语，可以放在句首，句中，句末，翻译为正如/正像)

The famous magician Liu Qian, as we all know, is from Taiwan.

众所周知，著名魔术师刘谦是台湾人。

There is a net bar around here, as I remember.

我记得这儿附近有一家网吧。

As is often the case, girls like dolls while boys like guns.

女孩子喜欢玩具而男孩子喜欢枪，这是常见的情况。

As is often the case, little boys tend to be very active and out of control.

Einstein, as we know, is a famous scientist.

As has been mentioned above, computers have many advantages .

Great changes have taken place in China, as is known to all.

There was a net bar around there, as I remember .

（2）which 引导的从句对主句所叙述的事情进行补充，表示会导致某种状态或结果.（表示，这一点，这件事情；与主句有种因果，并列关系放在主句之后，用逗号隔开.）

He changed his mind again, which made us all angry.

他又改变了主意，这使我们大家都生气了。

She tore up my photos, which (=and that) upset me.

她撕碎了我的照片，这使我很不安。

She stole her friend’s money, which(=and that) was disgraceful.

He tore up my photo, which(=and that) upset me.

He has passed the College Entrance Examination, which makes his parents quite happy.

（3）在从句中作定语或者介词的宾语，需要用which

Jenny might come, in which case I'll ask her.

詹妮可能会来，要是那样的话我就去问她。

She graduated from a local middle school, after which she went to Beijing University.

她毕业于当地的一所中学，之后她去了北京大学。

He was educated at the local grammar school , after which he went on to Cambridge.

Lily might possibly come, in which case I will ask her .

（4）不能省略非限制性定语从句的be 时，用which，反之用as

Jane told me she won the match, which was a lie.(不能省略）

As(was) planned, we met at the airport.(可省略助动词be)

（5）当从句是否定句或者从句谓语动词跟复合宾语时，一般用which不用as

He pretended not to know me, which I didn’t understand .

He admires everyone in the class, which I find quite strange

（6）当从句的谓语动词是否定形式或含着一个复合宾语时，一般用which而不用as。

He pretended not to know me, which I didn't understand.

他假装不认识我，这是我搞不明白的。

He admires everyone in his class, which I find quite strange.

他羡慕班里的每个学生，我认为太奇怪了