【高频考点8】 情态动词 ★★
情态动词 |
词义 |
否定式 |
缩略否定式 |
can/could |
能,能够;可能 |
can/could not |
can’t/couldn’t |
may/might |
可以;也许 |
may/might not |
mayn’t/mightn’t |
must |
必须;一定 |
must not |
mustn’t |
should |
应该 |
should not |
shouldn’t |
ought to |
应当 |
ought not to |
oughtn’t to |
shall |
应该;必定 |
shall not |
shan’t |
will/would |
愿意 |
will/would not |
won’t/wouldn’t |
need |
需要 |
need not |
needn’t |
dare |
敢 |
dare not |
daren’t |
have to |
不得不 |
do/does/did not have to |
don’t/doesn’t/didn’t have to |
used to |
过去常常 |
used not to/did not use to |
didn’t use to |
had better |
最好 |
had better not |
无 |
would rather |
宁愿 |
would rather not |
无 |
(一)高频考点:
1.Can
(1)cannot help but意为“不得不”,后接动词原形。例:
Due to the present price level, we cannot help but adjust our offer.
(2)cannot help意为“不禁,禁不住”,后跟名词或动词-ing形式。例:
I cannot help missing that girl.
(3)cannot...too...表示“无论怎样……都不过分”,“越……越好”(有时cannot可用can never代替)。例:
You cannot be too careful to cross the road.
You can never do the work too well.
2.Must/have to
(1)二者均表示“必须”,但must多表示主观意志,have to 多表示客观需要。例:
——I must keep my word.
——It rained heavily, so the children had to stay at home.
(2)have to 的否定式和疑问式需要助动词构成,not have to 相当于needn’t,意为“不必”。例:
You don’t have to/needn’t tell him the truth If you don’t want to.
(3)表示“必须”意义的must的一般疑问句回答。例:
——Must I hand in my composition today?
——No, you needn’t/don’t have to. / Yes, you must.
3.Should/Ought to
(1)should与ought to之间差别细微,should多表达自己的主观看法;ought to则多反映客观事实,在谈到法律、义务和规定(或要使自己的意见听起来像义务和法律一样有力)时常用ought to。
You should/ought to go and see your grandfather.
We ought to go and plant trees, but I don’t think we have time.
4.Used to
(1)used to do sth./be used to (doing) sth./be used to do sth.区别
used to do sth.表示过去的习惯,意为“过去常常做某事”,只能用于表示过去。例:
I used to go to the gym three times a week, but I don’t work out any more.
(2)be used to (doing) sth.表示“习惯于(做)某事”,有时态变化。例:
I’m used to getting up early.
I’m not used to eating so much at lunchtime.
(3)be used to do sth.是use sth. to do sth.的被动形式,意为“被用来做某事”,有时态变化。例:
This machine is used to cut up waste paper.
5.Had better
(1)had better...有命令口气,因而下级对上级或晚辈对长辈不宜用这种结构。比较有礼貌的说法是:It might be better for you...; It would be better for you...。例:
It might be better for you to help me, Grandpa.
(2)had better的否定式是在其后加not。例:
You’d better not do that again.
(3)had better的疑问句通常不以普通疑问句的形式出现,但有时用于否定疑问句,常用“Hadn’t+主语+better...?”结构,作为一种劝告形式,比肯定形式的语气更婉转一些。例:
Hadn’t you better take an umbrella?
Hadn’t you better ask him first?