2．關(guān)系代詞和關(guān)系副詞的選擇依據(jù)

　(1) 弄清代替先行詞的關(guān)系詞在從句中作什么成分,作狀語的應(yīng)選用關(guān)系副詞，作主語．賓語或表語的可選用關(guān)系代詞。

1．二者差異比較

　限制定語從句緊跟先行詞，同先行詞這間一般不加逗號，僅修飾先行詞，可以由關(guān)系代詞．關(guān)系副詞或that來引導(dǎo)。非限制性定語從句僅作補(bǔ)充或說明，用逗號與主句隔開，既可修飾先行詞，又可修飾整個主句，不可用that引導(dǎo)。

2. that可引導(dǎo)定語從句表示時間．地點(diǎn)或原因

　That有時可以代替關(guān)系副詞 when, where 或者why引導(dǎo)定語從句表示時間．地點(diǎn)或原因，在 that引導(dǎo)的這種定語從句中，that也可以省去。

1．關(guān)系副詞也可以引導(dǎo)定語從句

　 關(guān)系副詞在從句中分別表示時間．地點(diǎn)或原因。關(guān)系副詞when在從句中充當(dāng)時間狀語，where 充當(dāng)?shù)攸c(diǎn)狀語，why充當(dāng)原因狀語。

3．“介詞+關(guān)系代詞“是一個普遍使用的結(jié)構(gòu)

　(1) “介詞+關(guān)系代詞“可以引導(dǎo)限制性定語從句，也可以引導(dǎo)非限制性定語從句。“介詞+關(guān)系代詞“結(jié)構(gòu)中的介詞可以是 in, on, about, from, for, with, to at, of, without 等，關(guān)系代詞只可用whom或 which,不可用 that 。

　(2) from where為“介詞+關(guān)系副詞“結(jié)構(gòu)，但也可以引導(dǎo)定語從句。例如：

　 We stood at the top of the hill, from where we can see the town..

　(3) 像listen to, look at, depend on, pay attention to, take care of等固定短語動詞，在定語從句中一般不宜將介詞與動詞分開。例如：

　 This is the boy whom she has taken care of.

2．關(guān)系代詞的用法

　(1) 如果先行詞是all, much, anything, something, nothing, everything, little, none等不定代詞，關(guān)系代詞一般只用that，不用which。例如：

　All the people that are present burst into tears.

　(2) 如果先等詞被形容詞最高級以及first, last, any, only, few, mush, no, some, very等詞修飾，關(guān)系代詞常用that,不用which, who，或whom。例如：

　(3) 非限制性定語從句中，不能用關(guān)系代詞that,作賓語用的關(guān)系代詞也不能省略。例如：

　There are about seven million people taking part in the election, most of whom、are well educated.

　(4) which還有一種特殊用法，它可以引導(dǎo)從句修飾前面的整個主句，代替主句所表示的整體概念或部分概念。在這種從句中，which可以作主語，也可以作賓語或表語，多數(shù)情況下意思是與and this 相似，并可以指人。例如：

　He succeeded in the competition, which made his parents very happy.

　(5) that可指人或物，在從句中作表語，(指人作主語時多用who)僅用于限制性定語從句中。

　(6) which可作表語，既可指人，以可指物。指人時，一般指從事某種職業(yè)或是有種特征．品性或才能的人。Which引導(dǎo)的定語從句可以限制性的，也可以是非限制性的。

　(7) 如果作先作詞的集體名詞著眼于集體的整體，關(guān)系代詞用which;若是指集體中的各個成員，則用who。

　(8) 先行詞有兩個，一個指人，一個指物，關(guān)系代詞應(yīng)該用that。例如：

　The boy and the dog that are in the picture are very lovely.

　(9) 如果先行詞是anyone, anybody, everyone, everybody, someone, somebody,關(guān)系代詞應(yīng)該用 who 或whom，不用 which。例如：

　Is there anyone here who will go with you?

1. 關(guān)系代詞用來指代先行詞是人或物的名詞或代詞

　例1：This is the detective who came from London.

　例2：The book which I am reading is written by Tomas Hardy.

　例3：The desk whose leg is broken is very old.

　例4：This is the room that Shakespeare was born in.

帶to 的情態(tài)動詞有四個：ought to, have to, used to, be to, 如加上have got to ,(=must), be able to為六個,它們的疑問，否定形式應(yīng)予以注意：

Do they have to pay their bill before the end of the month?

She didn‘t use to play tennis before she was fourteen.

You ought not to have told her all about it.

Ought he to see a heart specialist at once.?

例：Tom ought not to ___ me your secret, but he meant no harm.

A.have told　　　　 B.tell　

C.be telling　　　　 D. having told

第4講：定語從句

用來說明主句中某一名詞或代詞(有時也可說明整個主句或主句中一部分)而起定語作用的句子叫作定語從句。

1) may(might) have + done sth, can (could) have + done sth表示過去，推測過去時間里可能發(fā)生的事情。

Philip may (might) have been hurt seriously in the car accident.Philip can (could) have been hurt seriously in the car accident.

2)　must have +done sth，對過去時間里可能發(fā)生的事情的推測，語氣較強(qiáng)，具有"肯定"，"諒必"的意思。-

--Linda has gone to work, but her bicycle is still here.

---She must have gone by bus.

3) ought to have done sth, should have done sth.本應(yīng)該做某事，而事實(shí)上并沒有做。否定句表示"不該做某事而做了"。You ought to (should) have been more careful in this experiment.　 He ought not to have thrown the old clothes away.(事實(shí)上已扔了。)

ought to 在語氣上比should 要強(qiáng)。

4) needn't have done sth　 本沒必要做某事　

I dressed very warmly for the trip, but I　needn't have done so. The weather was hot.

5) would like to have done sth　 本打算做某事　　

I would like to have read the article, but I was very busy then.

can, could, may, might, must 皆可表示推測，其用法如下：

1)情態(tài)動詞+動詞原形。

表示對現(xiàn)在或?qū)�來的情況的推測，此時動詞通常為系動詞。I don't know where she is, she may be in Wuhan.

2)情態(tài)動詞+動詞現(xiàn)在進(jìn)行時。

表示對現(xiàn)在或?qū)�來正在進(jìn)行的情況進(jìn)行推測。

At this moment, our teacher must be correcting our exam papers.

　這時，我們老師想必在批改試卷

3)情態(tài)動詞+動詞完成時。

表示對過去情況的推測。

We would have finished this work by the end of next December.明年十二月底前我們很可能已完成這項(xiàng)工作了。The road is wet. It must have rained last night.地是濕的，昨天晚上一定下雨了。

4)情態(tài)動詞+動詞的現(xiàn)在完成進(jìn)行時。

表示對過去正在發(fā)生事情的推測。

Your mother must have been looking for you.你媽媽一定一直在找你。

5)推測的否定形式，疑問形式用can't, couldn't表示�！�Mike can't have found his car, for he came to work by bus this morning.　邁克一定還沒有找回他的車，因?yàn)樵缟纤�是坐公共汽車來上班的�?

　注意：could, might表示推測時不表示時態(tài)，其推測的程度不如can, may。