贵州省思南中学高一下学期英语课件：必修三,Unit2,Healthy,eating--Grammar--Modal,verbs

a should ought to都可表示 应该应该 ought to用于表示按道理应应当 常指 客 观观的义务义务 或责责任 大多数情况下 可用 should代替 但比should语语气重 I should help her because she is in trouble You ought to take care of the baby b 表示劝劝告 建议议或命令时时 should 和ought to可通用 但在疑问问句中常 用 should ought to的否定式为为oughtn t to 或 ought not to You should ought to go to class right away Should I open the window What should we do next c should ought to 都可表示推测测 He ought to should be home by now This is where the oil ought to should be should和ought to后面跟动词动词 不定式的完 成 式 其肯定句表示 过过去应该应该 做而未 做 其否定句则则表示 过过去不该该做但做 了 You should ought to have made the decision a week ago I shouldn t have made such a foolish mistake 多数情况下 ought to可与should互 换换 使用 ought to的反意疑问问句用 shouldn t替代 2 must和have to must 的用法 1 表示主观观的义务义务 和必要 主要用于肯 定句和疑问问句 意思为为 必须须 得 要 由must引起的疑 问问 句 肯定回答要用must或 have to 否 定回答要用needn t 或 don t have to 意 思是 不必 must的否定形式mustn t表示禁止 意 思是 不能 不许许 如 Must I finish the task right now 我现现在必须须完成这这个工作吗吗 Yes you must Yes you have to 是的 No you needn t No you don t have to 不 不必 You mustn t come here without permission 未经经允许许 你不能来这这儿 have to的用法 1 must表示一种主观观的需要 而have to 表 示一种客观观的需要 意思是 不得 不 如 I have to attend an important meeting this afternoon 今天下午我不得不参加一个 重要的会议议 Mother is out so I have to look afterthe shop 妈妈妈妈 不在家 因此我不得不照看商店 2 have to的否定形式是 don t have to 相 当于 needn t 如 They don t have to buy a computer at present 他们们目前没有必要买电脑买电脑 3 must和need a need作情态动词时态动词时 只能用于疑问问句 和 否定句 构成否定句和疑问问句时时不借 助于助动词动词 do Need I finish the work today Yes you must No you needn t b must 的肯定形式表示 必须须 否 定式表示 禁止 严严禁 You must come here You mustn t take the book away from the library Choose suitable modal verbs below to complete the following dialogues ought oughtn t to should shouldn twill mustn t needn t don t have to can can t 1 Sam How can I grow thinner Mum Mum Well you h a v e t o eat food with plenty of fibre that helps you digest better And you s h o u ldstop drinking cola or eating sweet food Sam Does it mean I s h o u l d n t eat my favourite fried chicken any more Mum Not exactly if you love fried chicken you n e e d n t give it up Just eat it less often You d o n t h a v e t o n e e d n t s h o u l d n t worry too much a little fried chicken w i l ldo you good 2 Doctor You are sick because you ve eaten poisonous mushrooms Where did you get them Lucy I picked them in the forest I know we h a v e toeat fresh vegetables Doctor Oh but you m u s t n teat them until you re sure they are not poisonous Lucy Thank you doctor I ll be more careful next time 3 Charles I wish I could see things clearly in the dark Tom Eating carrots o u g h t tohelp you see better You s h o u l d eat some every day 3 Now work in pairs One of you asks a question The other answers it Then swap over Remember to use modal verbs in your dialogue Example S1 What should you do after school S2 I have to go home at once I need to take the bus I should do my homework Other possible questions are 1Do you know what you have to do when you borrow books from the library 2Do you know what to do when you teeth ache 3 Do you know what to do if you need to meet someone you don t know at the airport 4Do you know what to do if you want to get a discount in a shop 5Do you know what you should do when you meet the hostess in your friend s home Suggested answers to rcise 1 on page 50 1 have to should should 2ought to should 3 mustn t would 4 have to 5 can t can t