高中英语 Unit2 Healthy eating-Grammar 新人教版必修3
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thin after eating Yong Hui’s food… ➢ They would bee tired very quickly.
Modal verbs
a. should, ought to都可表示“应该”。 ought to用于表示按道理应当，常指客 观的义务或责任，大多数情况下可用 should代替，但比should语气重。
for our aged parents?
─You ____ do anything except to be with
them and be yourself. (重庆 2007)
A. don’t have to B. oughtn’t to
C. mustn’t
D. can’t
【点拨】根据题意“除了和他们呆在择don’t have to表示“不必”。
故选A项。
3. must和need a. need作情态动词时, 只能用于疑问句和
否定句。构成否定句和疑问句时不借 助于助动词do。 —Need I finish the work today? —Yes, you must. / No, you needn’t.
1) must表示一种主观的需要，而 have to表示一种客观的需要，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。
Mother is out, so I have to look after the shop.
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 puter at present.
他们目前没有必要买电脑。
【考例】The boss has given everyone a
You ought to have helped him with his English, ________? A. won’t you B. ought not you C. shouldn’t you D. wouldn’t you
2. must和have to must的用法 1) 表示主观的义务和必要, 主要用于肯
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。
He ought to / should be home by now. This is where the oil ought to / should be.
➢ He could not believe his eyes. ➢ Perhaps he should go to the library
and find out. ➢ He had better do some research! ➢ Even though her customers might get
定句和疑问句, 意思为 “必须……， 得……，要……”；由must引起的疑问句， 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”。如：
— Must I finish the task right now? 我现在必须完成这个工作吗？
注意
should 和ought to 后面跟动词不定式的完成 式, 其肯定句表示“过去应该做而未做”, 其 否定句则表示 “过去不该做但做了”。 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互换使用。 ought to的反意疑问句用shouldn’t替代。
—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 e here without permission.
未经允许，你不能来这儿。
have to 的用法
Grammar
Find the sentences containing modal verbs in the reading passage.
•Then usually by lunchtime they would all be sold. •What could have happened? •Nothing could be better…” •Something terrible must have happened if …
b. must的肯定形式表示“必须”，否定 式
special holiday, so we ____ go to work
tomorrow. (上海 2007春)
A. can’t
B. mustn’t
C. needn’t
D. shouldn’t
【点拨】考查情态动词。根据题意, 可知
这里表示“没有必要”, 故只能选C项。
【考例】─What do you think we can do
I should help her because she is in trouble. You ought to take care of the baby.
b. 表示劝告、建议或命令时，should和 ought to可通用，但在疑问句中常用 should。ought to的否定式为oughtn’t to或ought not to。
Modal verbs
a. should, ought to都可表示“应该”。 ought to用于表示按道理应当，常指客 观的义务或责任，大多数情况下可用 should代替，但比should语气重。
for our aged parents?
─You ____ do anything except to be with
them and be yourself. (重庆 2007)
A. don’t have to B. oughtn’t to
C. mustn’t
D. can’t
【点拨】根据题意“除了和他们呆在择don’t have to表示“不必”。
故选A项。
3. must和need a. need作情态动词时, 只能用于疑问句和
否定句。构成否定句和疑问句时不借 助于助动词do。 —Need I finish the work today? —Yes, you must. / No, you needn’t.
1) must表示一种主观的需要，而 have to表示一种客观的需要，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。
Mother is out, so I have to look after the shop.
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 puter at present.
他们目前没有必要买电脑。
【考例】The boss has given everyone a
You ought to have helped him with his English, ________? A. won’t you B. ought not you C. shouldn’t you D. wouldn’t you
2. must和have to must的用法 1) 表示主观的义务和必要, 主要用于肯
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。
He ought to / should be home by now. This is where the oil ought to / should be.
➢ He could not believe his eyes. ➢ Perhaps he should go to the library
and find out. ➢ He had better do some research! ➢ Even though her customers might get
定句和疑问句, 意思为 “必须……， 得……，要……”；由must引起的疑问句， 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”。如：
— Must I finish the task right now? 我现在必须完成这个工作吗？
注意
should 和ought to 后面跟动词不定式的完成 式, 其肯定句表示“过去应该做而未做”, 其 否定句则表示 “过去不该做但做了”。 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互换使用。 ought to的反意疑问句用shouldn’t替代。
—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 e here without permission.
未经允许，你不能来这儿。
have to 的用法
Grammar
Find the sentences containing modal verbs in the reading passage.
•Then usually by lunchtime they would all be sold. •What could have happened? •Nothing could be better…” •Something terrible must have happened if …
b. must的肯定形式表示“必须”，否定 式
special holiday, so we ____ go to work
tomorrow. (上海 2007春)
A. can’t
B. mustn’t
C. needn’t
D. shouldn’t
【点拨】考查情态动词。根据题意, 可知
这里表示“没有必要”, 故只能选C项。
【考例】─What do you think we can do
I should help her because she is in trouble. You ought to take care of the baby.
b. 表示劝告、建议或命令时，should和 ought to可通用，但在疑问句中常用 should。ought to的否定式为oughtn’t to或ought not to。