2. that 與 which的用法區別。兩者都可指物，常可互換。其區別主要在于：

(1) 引導非限制性定語從句時，通常要用which：

She received an invitation from her boss, which came as a surprise. 她收到了老板的邀請，這是她意想不到的。

(2) 直接放在介詞后作賓語時，通常要用which：

The tool with which he is working is called a hammer. 他干活用的那個工具叫做錘子。

(3) 當先行詞是下列不定代詞或被它們修飾時much, little, none, all, few, every(thing), any(thing), no(thing) 等時，通常用that：

There was little that the enemy could do but surrender. 敵人無法,只有投降了。

All [Everything] that can be done must be done.  凡能做的事都必須做。

(4) 當先行詞有the very, the only, the same 等修飾時，通常用that：

This is the only example that I know. 我知道的例子只有這一個。

Those are the very words that he used. 那是他的原話。

(5) 當先行詞有形容詞最高級或序數詞(包括last, next等)等修飾時，通常用that：

This is the best dictionary that I've ever used. 這是我用過的最好的詞典。

The first thing that you should do is to work out a plan. 你應該做的第一件事是訂個計劃。

(6) 當關系代詞在定語從句中用作表語時，通常用that：

China is not the country (that) it was. 中國已不是過去的中國了。

(7) 當先行詞是一個既指人又指物的并列詞組時，通常用that：

They talked about the persons and things that most impressed them. 他們談論了使他們印象最深的人和事。

(8) 當要避免重復時：

Which is the course that we are to take? 我們選哪門課程？

3. that與who的用法區別。

(1) 兩者均可指人，有時可互換：

All that [who] heard him were delighted. 所有聽了他講話的人都很高興。

Have you met anybody that [who] has been to Paris? 你遇見過到過巴黎的人嗎?

He is the only one among us that [who] knows Russian.他是我們中間唯一懂俄語的人。

(2) 但是在下列情況，通常要用 that：

①當先行詞是一個既指人又指物的并列詞組時：

I made a speech on the men and things that I had seen abroad. 我就我在國外所見到的人和事作了報告。

②當先行詞是who時(為避免重復)：

Who was it that won the World Cup in 1982? 誰贏得了1982年的世界杯？

③當關系代詞在定語從句中作表語時(可省略)：

Tom is not the boy (that) he was. 湯姆這孩子已不是以前那個樣子了。

4. as與which的用法區別

(1) 引導限制性定語從句時，在such, as, the same后只能用as，其他情況用 which：

I never heard such stories as he tells. 我從未聽過他講那樣的故事。

It's the same story as I heard yesterday. 這故事跟我昨天聽到的一樣。

This is the photo which shows my house. 這張照片拍的是我的住宅。

(2) 引導非限制性定語從句時，有時兩者可互換：

I live a long way from work, as [which] you know. 我住得離工作單位很遠，這你是知道的。

(3) 但在，在以下情況引導非限制性定語從句時，兩者不可換用：

① 當從句位于主句前面時，只用 as：

As is known to everybody, the moon travels round the earth once every month. 月球每月繞地球轉一周，這是每個人都清楚的。

② as 引導的非限制性定語從句應與主句在意義上和諧一致，which無此限制：

He went abroad, as [which] was expected. 他出國了，這是大家預料到的。

He went abroad, which was unexpected. 他出國了，這讓大家感到很意外。(不用as)

③ as 引導非限制性定語從句時，先行詞通常不能是主句中某個具體的詞，而應是整個句子、整個短語或某個短語推斷出來的概念，而which 則無此限制：

The river, which flows through London, is called the Thames. 這條流經倫敦的河叫泰晤士河。(不用as)

④ 當as 引導非限制性定語從句作主語時，其謂語通常應是連系動詞，而不宜是其他動詞，而 which則無此限制：

She has married again, as [which] seemed natural. 她又結婚了，這似乎很自常。

She has married again, which delighted us. 她又結婚了，這使我們很高興。(不用as)

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