情态动词惊讲
,在英文中主要用来表示说话人的看法、态度等.它很接近中文里的能愿动词.从用法上来说,它有这样几个特点：
1）各个情态动词自身都有一定的词义.
2）情态动词不能在句中独立担当谓语.
3）情态动词在句中不受任何人称,性,数变化的影响.
4) 情态动词后接的不定式（除ought外）都不带to ,即接动词原形.
英文中的情态动词主要有：can ,could ; may ,might ; must ; ought ; need ; dare ,dared ,另外,shall ,will ,should ,would在一定的场合也可用作情态动词.例如：
He can speak five languages .他会说五种语言.
She must have arrived home by now .现在她准到家了.
We should study hard for our motherland .我们应该为祖国而努力学习.
They needn't be in such a hurry for there is enough time
for them .他们还有足够的时间,用不着这么慌张.
1.常用情态动词的基本用法
can ,could 能,会
（could可以看作是can的过去式,这两个词除了时态不相同外,在表达意思的许多方面是相同的.当然could也有自己独特的用法.）
1）表示脑力或体力上的能力
Nobody can stop the development of science .
谁也无法阻止科学的发展.
She can sing that song in English.她能用英文唱那歌.
He can submerge to a depth of about twenty meters .
他能潜入约二十米深的水中.
He could hardly support his family before he found the new job .他在找到那份新工作前几乎无 法养家.
I could not understand the lecture on the computer given by Mr.Smith .
我听不懂史密斯先生作的那个关于计算机的讲座.
2)表示客观上的可能性
You can borrow this useful book from the library .
你可以从图书馆借到这种有用的书.
A more suitable person than him for the job can not be found .不可能找到比他更适合这份工作的人了.
Now people can skate on the lake .现在人们可以在湖上滑冰了.
When the storm stopped ,the plane could take off .
当风暴停下来时,飞机可以起飞了不得.
3)表示主观上的允许
Can I ask you some questions about it
我可以问你有关这件事的几个问题吗?
You can not leave here till I come back .直到我回来你才能离开.
Such kind of thing can't happen any more later .
这类事以后不准再发生了.
Can you tell me how to get to the airport 你能告诉我怎么去机场吗?
Could you tell me how to get to the airport
您能告诉我怎么去机场吗?
Could I be forgiven my negligence 请原谅我的疏忽,行吗?
4）（用于否定句、疑问句或感叹句中）表示猜测、怀疑或惊诧
How can / could you be here 你怎么会在这儿?
She couldn't / can't be so stupid to do that .
她不可能蠢得去做那种事吧.
He couldn't / can't be over seventy .他不可能有七十多岁了.
Where could / can the boy be now 那孩子现在能在哪儿呢?
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