情 态 动 词
一、一般疑问句中几个情态动词的问与答
1. Need I/he/…?
Yes,you/he/…must.(不用need)
2. Must I/ he/…?
No,you/ he/…needn’t/don’t(doesn’t,won’t)have to.(不用mustn’t)
3. May I/ he/…?
No,you/ he/…mustn’t.(少用may not)
4. Could(Can)you…?
Yes,I can (不用could)
5. Shall I/she/ he…?
No,you(she,he)needn’t/can’t/mustn’t
二、情态动词表“推测”
1.can,may,must使用的句式：
1)肯定陈述句中：must表“肯定、必定、一定”意，may/might表“也许，或许”意。
2)否定陈述句中：can’t/couldn’t表“不可能”意，may not/might not表“也许不、可能不”意。
3)疑问句中：只能用can或could,不能用must,may或might。
注意：表推测的could,might并不是指过去时间，而是表示比can,may把握性略小些的情况。
2.对目前状态的推测：
1)must/may/might/can/could＋be＋表语
例如：She must be a teacher.她肯定是老师。She can’t/couldn’t be a doctor.她肯定不是医生。 He may not/might not be a doctor.他可能不是医生。
2)must/may/might/can/could＋一些不能用于进行时的静态动词(如:have,exist,live,like,hate,own,belong to等)
例如：She must have her own car,for she has a lot of money.
That kind of bird may live in the valleys.
3.对目前正在发生的事情进行推测：
句式：must/may/might/can/could＋be doing
例如：They must be waiting for us.他们肯定正在等我们。
She may/might be doing her homework.她可能正在做作业。
Can/Could he be playing football?他会正在踢足球吗？
4.对已发生的事情进行推测：
句式：must/may/might/can/could＋have done
例如：There’s no lignt in the room. They must have gone to bed./She knows nothing about the film. She can’t/couldn’t have seen it./Can/Could he have been a doctor?/He may/might(not)have been a teacher./They must have been watching TV at nine last night./Can/Could she have stayed in Beijing last year?
注意：will have done句式也可表“肯定/可能已经…”推测意。
例如：He will have learned advanced mathematics,for he knows a lot about it. 他肯定/可能学过高等数学，因为他对此懂得很多。
三、“情态动词＋have done”用法
1.should/ought to ＋have done,意“本应该…”，含有责备或后悔意。
例如：You should have come here a little earlier./I ought to have sent him to school./
2.shouldn’t/oughtn’t to＋have done,意“本不应该”，含有责备或后悔意。
例如：You shouldn’t have watered the flower./I oughtn’t to have scolded her for such a small thing.
3.might have done,意“过去可能做”；could have done意“本能够做”，两者都含有委婉批评或遗憾之意，也可表对过去情况的推测。
例如：He might have gone to Nanjing with Professor Wang.last week,but he was ill.上星期他本可以和王教授一起去南京的，可他病了。We could have finished the work ahead of time.我们本来是能够提前完成工作的。
四、情态动词在反意疑问句中的用法
1.“肯定祈使句＋附加问句”结构，附加问句常用will/would/won’t you形式。
例如：Stand still,will/would/won’t you?
2.“否定祈使句＋附加问句”结构，附加问句常用will/would you形式。
例如：Don’t watch TV,will/would you?
3.Let’s…,shall we? ; Let us…,will/won’t you?
4.含有must句子的反意问句
1)must表示“必须”时，附加部分常用needn’t,也可用mustn’t.例如：He must go with you,needn’t/mustn’t he?
2)mustn’t表“一定不能”时，附加部分用may.例如：She mustn’t leave,may she?
3)must表“一定、想必”推测意时，附加部分主要有下列几种形式：
A.He must be an engineer,isn’t he?They must be writing now,aren’t they?(这类句子问句前部分含“must be…”或“must be doing…”。)
B.She must have a car/live there, doesn’t she?
C.He must have seen the film,hasn’t he？(这类句子问句前部分的谓语为must have done,句子无具体过去时间状语。)
D.He must have seen the film last week,didn’t he?(这类句子问句前面部分的谓语为must have done,句子有具体过去时间状语。)
E.Mother must have been shopping then,wasn’t she?(前面部分谓语为must have been doing。)
5.含有may表推测的句子，其反意问句形式与must表推测的反意问句形式相似。
例如：She may have finished her homework,hasn’t she?
五、几组词语辨析
1.must与have to:must强调说话者的主观看法，have to强调客观需要，表示“不必”意要用needn’t或don’t/didn’t/won’t have to,不能用mustn’t。
2.can/could与be able to:can多用于现在时，也可用于将来时，could只用于过去时，be able to可用于各种时态。表示“过去经过努力而做成(或没做成)”要用was/were(not) able to ，而不用could(not)。例如：He worked hard,but he wasn’t able to pass the exam.
3.will,would,used to:都可表“习惯”意。①will表示不受时间限制的习惯性动作。如：Fish will die out of water./ She’ll sit for hours without saying anything.
②would表示过去习惯性的动作，但不涉及与现在情况的对比。如：He would walk by the river in the morning.注意：would后不能跟表状态动词。例如不能说He would be late for school last year. ③used to表示过去习惯性的动作或状态，但这种习惯现在已不存在了。如：He used to get up early. He used to be late for school.
情态动词考点分析
1.－Could I borrow your dictionary? (NMET)
－Yes,of course you________.
A.might B.will C.can D.should
析：B、D意明显不合；A语气不妥，与of course不符。此题Could是表Can意的委婉说法，并非过去时，所以答案应为C。
2.－Shall I tell John about it?
－No,you_________.I’ve told him already. (NMET)
A.needn’t B.wouldn’t C.mustn’t D.shoudn’t
析：B意明显不合用，可排除。mustn’t意“不许、不得”，shouldn’t意“不应该”都不合情景。只有needn’t表“不必”与下文“I’ve told him already”相贴切。
3.－There were already five people in the car,but they managed to take me as well.
－It_________a comfortable journey. (NMET)
A.can’t be B.shouldn’t be
C.mustn’t have been D.couldn’t have been
析：A、B是对现在情况而言，与情景不合。表否定推测不能说mustn’t have been,只有D选项“不可能是”意思切合，时态也对，故为正确答案。
4.The fire spread through the hotel very quickly ，but everyone________get out.
(NMET)
A.could B.would C.was able to D.had to
析：根据题干提供的情景B、D皆应排除。在A、C两选项中，因为根据情景要选一个“经过努力能够”这样意思的词，故定答案为C。
5.I told Sally how to get here,but perhaps I________for her.
A.had to write it out B.must have written it out
C.should have written it out D.ought to write it out
析：A项意“(当时)不得不写出来”，不合题意；D项意“(现在)应写出来”也不合题意；B项意“(当时)肯定已写出来”明显不对。只有表“当初应该写出来”意的C项才合上下文。
6.That young man has made so much noise that he_________not have been allowed to attend the concert. (上海高考题)
A.could B.must C.would D.should
析：若选A。意“不可能已被允许…”与情景不合，应排除；B项不可选；C项意“当时将不会被允许…”也与情况相悖。只有D“should not have been allowed…”表示“当初不该让他…”才合题意。
7.－Can I help you,sir?
－Yes,I bought this radio here yesterday,but it______.(NMET)
A.didn’t work B.couldn’t work C.can’t work D.doesn’t work
析：若选A。意“昨天不响（今天响了）”，不合题目情景；若选B。其意是“当时不能工作（现在能工作了）”，显然不合题；若选C。意为“这台收音机根本不能工作（是废品）”这未免显得武断；只有D表“这台机子不响（有毛病）”意才能合理地表达来找商店服务员的原因。