情态动词有没有事态的变化

Question

情态动词有没有事态的变化

Answer 1

情 态 动 词 的 时 态
英语中情态动词也象行为动词一样,具有时态的变化.现根据情态动词的功能分述如下：
一、“能力”表示现在或将来的“能力”用can + 动词原形；表示过去的“能力”用could + 动词原形：
A computer can’t think for itself , it must be told what to do .
Can you join us tomorrow?
He could speak five languages when he was young .
表示将来的“能力”时用shall / will be able to 更能把时间关系表示明确.
二、“允许”表示现在或将来的“许可”,陈述句中用 can / may（不用could / might ）+动词原形,疑问句中用can /could / may / might +动词原形；表示过去的“许可”用could / might + 动词原形：
Could / Might / Can / May / I borrow your umbrella?
You may / can watch TV after you finish your homework .
He said I could go with him .
三、“禁止”表示现在的“禁止”用can't / mustn't / may not + 动词原形；表示过去的“禁止”用couldn't / mustn't +动词原形：
The guard said we mustn't / couldn't crossthe border.
You mustn't / can't / may not pick any flowers in the garden .
四、“必须”表示现在或将来的“必须”用must + 动词原形；表示过去的“必须”用had to / must +动词原形：
We must go early tomorrow .
Must we do it now?
She told me that she must / had to warn me of the danger .
五、“可能”表示现在或将来可能用can / could /may / might have + 过去分词；表示可能正在进行用can / could / may / might be + 现在分词：
He may / might / could leave tomorrow .
Might / Could / Can this be true?
He may not / mightn't /can't /couldn't have been at home last night .
They can't be working in the fields.
情态动词表示“可能”时,can 一般不用于肯定句,may 一般不用于疑问句,may not / mightn’t 表示“可能不”,can’t 表示“不可能”.
六、“肯定”表示现在肯定用must + 动词原形；表示过去肯定用must have + 过去分词；表示肯定正在进行用must be + 现在分词：
Jan’s light is on .She must be at home .
It must have rained last night ,for the ground is wet .
They must be reading in the reading room .
must 表示“肯定”时不能用于否定句,也不能表示将来.指将来肯定用be sure to :
He is sure to come tomorrow.
七、“必要”和“不必”表示现在或将来“必要（不必）”用need(n’t ) + 动词原形；表示过去用need (n’t )have + 过去分词；表示正在进行用need ( n’t ) be + 现在分词：
Need I clean the room today ?
Need you have told him about my plans ? 你把我的计划告诉了他有这个必要吗?
You needn’t have gone there . 你本不必去那儿的.
need 一般不用于肯定句need(n’t ) have + 过去分词与didn’t need + 不定式含义有所不同,前者表示某事过去没有必要做但却做了,后者表示某事不必要做（不论是否做了）.试比较：
A : I’ve brought my recorder.
B : But I’ve already got one .
A : Oh , so I needn’t have brought it .
A : I started off to walk , but Peter gave me a lift .
B : Oh , so you didn’t need to walk after all .
八、“（不）应该”表示现在或将来（不）应该做某事用should(n't ) / ought ( n't ) to + 动词原形；表示过去本该或不该做了某事用should (n't) / ought (n't ) to + have +过去分词；表示应该或不该正在做某事用should ( n' t ) / ought (n't ) to + have + 过去分词：
You ought to / should have helped him yesterday.
We should / ought to help each other .
He shouldn't / oughtn't to have cheated in the exam .
This is what I should / ought to be doing .
九、“（不）敢”表示现在“（不）敢”用dare + 动词原形；表示过去“（不）敢”用dare (d) + 动词原形,或dare have + 过去分词：
Dare you do it ?
I daren't ask you because I thought I must be wrong .
I didn't like their new house , though I daren't have said so .
dare 作为情态动词一般不用于肯定句.
十、“习惯”表示现在的习惯用will + 动词原形；表示过去的习惯用would / used to + 动词原形：
He used to / would get up at five when he lived with us .
In fine weather he will often sit in the sun for hours .