1、Grammar
情态动词用法巧析
【概念陈述】
情态动词本身有意义, 但不能单独作谓语, 必须和不带to的动词不定式一起构成谓语, 没有人称和数的变化，主要表示不同程度的肯定和必要性。多数情态动词有过去式。
【句例呈现】
1. A computer can’t think for itself; it must be told what to do.
2. The fire spread through the hotel very quickly but everyone was able to get out.
3. They will be able to run thi
2、s machine on their own in three months.
4. That big hall can seat 2,000 people.
5. —Could he borrow your computer?
—Yes, of course he can. / No, he can’t.
6. —Might I listen to music after supper?
—Yes, you may. / No, I’m afraid you may not.
7. You needn’t return the dictionary now. You can ke
3、ep it till next week if you like.
8. Johnny, you mustn’t play with the knife;you may hurt yourself.
9. —Will your brother stay together with us tonight?
—Sorry, he can’t. His teacher is coming to see him.
10. —May I ride my bike in the yard?
—No, you mustn’t.
11. You shouldn’t / oughtn’t to sa
4、y things like that to Granny.
【用法小结】
我们可以把上面的例句分类：
1-4句中can, could, be able to表示能力。be able to 能用于各种时态；can用来表示现在的或一般的能力。could 用来表示过去的一般的能力。而要表达将来的能力时，需用will be able to。was / were able to 表示某人在某一场合设法做了某事，相当于 managed to do sth. / succeeded in doing sth.。
5-6句中may / might, can / could用来表示请求允许。may
5、 / might比can / could 更为正式。can / may也用来表示给予许可; can’t / may not用来表示拒绝给予许可或禁止；must not也用于表示禁止，比may not较为有力；could不用于给予许可或者拒绝许可；might很有礼貌，不常用，主要用在间接引语里。
7-11句是表示否定的情态动词的用法。mustn’t 不准，禁止；needn’t没必要(= don’t have to)；can’t不能，不可能；may not不可以，可能不；shouldn’t不应该 (= oughtn’t to)
【重点剖析】 情态动词shall, will 的多种意义。
6、 shall, will均可表示将来。过去时分别为 should, would。shall用在主语是第一和第三人称的疑问句中表示征求对方的允诺；shall用于第二或第三人称陈述句时表示说话人给对方命令、警告、允诺、决心、威胁等；shall用于条约、规定、规章等文件中表义务，用于第三人称。 will用在主语是第二人称的疑问句中，表示“请求”；will用于主语是各人称的陈述句中，表示“意愿、倾向”。例如：
1. —The phone is ringing.
—I’ll get it.
2. The man shall be accused of murder if someone provided valid evidence.
3. They are not going to quarrel at all if you will only let them speak one by one.
4. —Sir, shall he go or stay?
—Let him go.
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