高中英语Unit5 SectionⅢGrammar__情态动词和过去将来时课件新人教版必修第三册

议
The cookies Susan made are delicious，you ought to try
some.
Would you recommend the play to other people?
表示愿望 I would like to know the date. I'd love to go to your birthday party.
I'd rather not pay you now.
表示义务和 You must come at once.
需要
We have to wear uniforms at school. I ought to be on my way.
4.情态动词难点透视 英语中的情态动词虽然为数不多，但是要掌握好它们的用法并不 容易。下面结合同学们在使用情态动词时不易掌握的难点谈几点看 法。
Unit 5 THE VALUE OF MONEY
Section Ⅲ Grammar——情态动词和过去 将来时
突破 语ቤተ መጻሕፍቲ ባይዱ大冲关
一、复习情态动词 情态动词表示说话人对某一动作或状态的态度。初中阶段大家已 经学习了一些情态动词，这里将对情态动词的特征、功能和用法进行 总结。
[观察例句] 1．Oliver believes that with a million-pound bank note a man could live a month in London. 2．Young man，would you step inside a moment，please? 3．May we ask what you're doing in this country and what your plans are?
(6)should 除表示必要或义务外，还可表示推测或可能。如： The American friends should be here now. “should/ought to＋have＋过去分词”既可表示本该做而事实上 没有做的事，也可以表示惊讶、责备、赞叹等情绪。如：
You should have told her about it the day before yesterday. It's wonderful that you should have achieved so much in these years. “情态动词＋have＋过去分词”是很重要的一种句型，除 should 外，may，might，must，couldn't，needn't，ought to 等都可以用于这 一句型，但要注意使用不同的情态动词句子的意思就有所不同。
The minister must have arrived in Shanghai，hasn't he?
(4)shall 可以用来征求对方意见，用于第一、三人称。此外它也 可以用来表示说话人的命令、警告、允诺、威胁或决心等，这时它用 于第二、三人称。如：
Shall she go to the concert with us this evening？(征求意见) You shall go to the front at once.(命令) Don't worry.You shall get the answer this very afternoon.(允诺) He shall be sorry one day.I tell you.(警告) Nothing shall stop us from fighting against pollution.(决心)
(2)must 与 have to 都可以表示“必须”的意思，但要注意以下两 点区别。
①must 只有现在时，而 have to 有现在时、过去时和将来时。如： We must work hard，or we'll fail in the examination.Years ago，the poor girl had to leave school for lack of money. ②must 表示主观看法，have to 则侧重于客观需要。如： We must be strict with ourselves in everything.In cities with many cars，some people have to wear masks.
She is your mother，so you ought to support her. We ought to go and see Mary tomorrow，but I don't think we will.
(8)need 用作情态动词，仅用于否定句和疑问句，而不用于肯定 句。在肯定句中要用 must，have to，should，ought to 或将 need 当作 行为动词使用。如：
②“must＋have＋过去分词”用来表示对已经发生的事情进行推 论。如果句子中有过去的时间状语，疑问部分用助动词 didn't；否则， 疑问部分用 haven't 或 hasn't。如：
The children must have watered the tomatoes yesterday，didn't they?
(7)ought to 与 should 意思接近，大多数情况下二者可以互换，但 是 should 谈的是自己的主观看法，ought to 则更多反映客观情况，在 谈到法律、义务和规定时使用。如：
We should/ought to help each other and learn from each other in our work.
③在过去时态的肯定句中需要某种条件或努力做成某事，我们要 用 was/were able to 而不能用 could。如：
It was a holiday and the children were able to go to the seaside. The girl worked hard so she was able to pass the final test.
You can go off duty now.
表示许可或 You can't open it until two o'clock.
禁止
You may not smoke here. You shouldn't take her help for granted.
You mustn't do that.
We need report the matter to the boss immediately.(误) We must report the matter to the boss immediately.(正) We need to report the matter to the boss immediately.(正)
may might must dare
may not might
not must not
dare not
/
will will not
won't
mightn't would would not wouldn't
mustn't need daren't ought to
need not ought not to
(3)must 表示推测时，其反意疑问句有好几种形式。①“must＋ 动词原形”对目前的情况进行推测时以及用 must＋be＋v.­ing 形式 对目前正在发生的情况进行推测时，疑问短语部分要与 must 之后的 动词相一致。如：
The mathematics teacher must be in the office now，isn't he?
needn't oughtn't to
3.情态动词的主要表意功能
用法
例句
表示能力 The little boy can read and write. I could feel the ground shaking.
Those of you who are familiar with the game will know this. 表示可能和 They made a bet which would settle their argument. Oh，you must be Sylvia's husband. 推测 It may seem lucky to you but not to me. That might not be true. There ought to be enough space for all of us.
(5)在表示将来的时间、条件状语从句中，不能用 will(这时的 will 不是情态动词，而是助动词，帮助构成将来时)。如：
If it will rain tomorrow，we shall not go to the mountain village.(误) If it rains tomorrow，we shall not go to the mountain village.(正) 当情态动词 will 表示意愿或决心时，是可以用于条件状语从句 的。如： If you will listen to me，I'll give you some advice on how to learn English. If you will come this way，the manager will meet you.
表示发出指 Will you please take her to the library?
Could you offer me work here? 示或提出请
Can I ask a question?
求
May we ask what you're doing in this country？
表示提出帮 Will you stay for lunch?
Wouldn't you like to come with me? 助或发出邀
May I help you?
请
Shall I put it in a box？
You could ask the teacher for help.
表示提出建 You should write him a letter.
(1)①can 表示可能性时，指的是理论上的可能，它通常不用来表 示某事实际发生的可能性或真实性。如：
Accidents can happen.Anybody can make mistakes. 如果我们要表达某事发生的实际可能性，要用 may，could 或 might 等。
We may spend our summer holidays in Hangzhou this year. Will you answer the telephone ？ It could/may/might be your mother. ②could 用来征求意见时，语气要比 can 委婉，但在回答问题时 我们不能用 could，因为语气委婉，可能性就变小了。如： —Could I use your telephone? —Yes，please go ahead.
(3)在用法上，情态动词与助动词一样，需后接动词原形，构成 谓语动词。
2．情态动词的否定式及缩略形式
情态动 词
否定式
缩略形 情态动
式
词
否定式
缩略形式
can could
cannot/ can not could not
can't couldn't
shall sould
shall not shan't should not shouldn't
[归纳用法] 1．情态动词的基本特征 (1)在形式上，情态动词没有实义动词的各种变化，只有 could， would，had to，might 等几个过去式，其他情态动词如 must、ought to 等的过去式皆与现在式同形。
(2)在意义上，大多数情态动词有多个意义，如 can 可以表达“能 力；可能；许可”等。
4．I can't say that I have any plans. 5．Anyway，I didn't dare to try again. 6．You mustn't worry about that. 7．If you'll excuse me，I ought to be on my way.