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一、 情态动词的特征和形式
A.情态动词的各种形式见下表：
情态动词
may
might
can
could
must
have to
ought to
will
would
shall
should
need
dare
used to
否定式
may not
might not
cannotcan not
could not
must not
do not have to
ought not to
will not
would not
shall not
should not
need not
dare not
used not to
did not use to
简略否定式
mayn't（老式英语，现在不常见）
mightn't
can't
couldn't
mustn't
don't have to
oughtn't to（否定句中to可省略）
won't
wouldn't
shan't（只用于英国英语）
shouldn't
needn't
daren't
usedn't to
didn't use to
B．情态动词除ought
to, used to等外，后面只接不带to的不定式。
1．情态动词+do
You shouldn't be so careless.你不该这样粗心大意。
Jessica told him yesterday she might not go on the trip.
杰西卡昨天告诉他，她可能不去旅行了。
Difficulties can and must be overcome.
困难能够而且必须克服。
2．情态动词+be doing
She must be listening to pop music.
她肯定在听流行音乐。
You should be reviewing your lessons.
你应该在复习功课。
My mother maymight be cooking now.
我妈妈可能正在做饭。
3．情态动词+have done
They might have visited the Great Wall.
他们可能参观过长城了。
He must have got up very early to catch the train.
他一定起得很早去赶火车了。
You ought to have come earlier.
你本该早一点儿来。
4．情态动词+be done
This word can also be used as a verb.
这个词也可以用作动词。
Something must be done to stop pollution.
必须采取措施来制止污染。
The work ought to have been finished long ago.
这工作早就该完成了。
C.情态动词第三人称单数一般现在时没有词形变化。
You ought to wear a raincoat.
你应该穿件雨衣。
She ought to wear a raincoat.
她应该穿件雨衣。
Plants must have oxygen in order to live.
为了存活植物必须有氧气。
A plant must have oxygen in order to live.
为了存活植物必须有氧气。
D.情态动词的时态并不是区分时间的主要标志。在一些场合中，情态动词的现在式和过去式都可以表示现在时间、过去时间或将来时间。
I'm afraid it might rain tonight.
我看今晚可能要下雨。
Could I borrow your thermos
我可以借用你的暖水瓶吗？
It's a nice day today. We could go for a walk.
今天天气不错，我们可以出去散散步。
E.情态动词是互相排斥的，一般不允许两个意义相近的情态动词连用。
【误】Soldiers must have to
obey orders.
【正】Soldiers have to obey orders.
军人必须服从命令。
【正】Soldiers must obey
orders.
军人必须服从命令。
【误】Can I be able to borrow
two books at a time
【正】Can I borrow two books at a time
我能一次借两本书吗？
【正】Will I be able to borrow
two books at a time
我能一次借两本书吗？
一、 情态动词的意义和用法
A. may和might
1．表示请求、许可，常译为“可以”。
在口语中可用can,
could代替may，但在正式场合用may。表示允许时，也可用might代替，might不表示过去时，而是表示口气比较婉转。
You may
take this seat if you like.
如果你喜欢可以坐这个位置。
MayCan
Could Might I have a talk with you
我可以和你谈谈吗？
---
MayMight I come into the room to see my mother
我可以进房间看我母亲吗？
--- No,
you mustn't. She needs to have a good rest.
不，你不能进。她需要好好休息。
提示：
May I ...问句常见的肯定回答和否定回答。
肯定回答
Yes, please.
Certainly.
Yes, of course.
Sure.
Go ahead, please.
否定回答
No, you can't.（最常见）
No, you mustn't.（具有强烈禁止的意思）
Please don't. You'd better not.
I don't think you can.
I'm sorry it's not allowed.
2．表示推测，可译为“可能，也许”。
Your
math teacher maymight be in his office.
你们的数学老师可能在办公室里。（一般情况下，might表示的可能性很小）
The
light isn't on. It maymight be broken.
那盏灯没有亮，它可能坏了。
There
may might be some ink left in the bottle.
瓶子里也许还剩点儿墨水。
注意：
用may表示推测一般不用于疑问句，在疑问句中通常用can来代替。
Can he
be at home
他可能在家吗？
--- Can
it be true
这可能是真的吗？
--- It
may be, or may not be.
可能是，也可能不是。
3．用在目的状语从句中，构成谓语。
He wants
to take a taxi so that he may get there in time.
他想坐出租车，这样他就能及时到达那里。
I
arrived at the airport earlier in order that I might meet him.
我早早地就到了机场为了能接到他。
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