1、情态动词表义务和需要语法精讲典例精析典例精析1. must可用来表义务，翻译为“必须”。例：I dont like this TV set. We must buy a new one. He must work hard to achieve his goals.情态动词表义务（1）典例精析典例精析2. have to可用来表义务，翻译为“不得不”。强调，并且。例：Im very tired and I have to stop to rest for a while. He had to stay in bed because of his illness.情态动词表义务（2）典例精析典例
2、精析3. shall用于条约，规定，规章等文件中。表示，多用于中。例：Its required in our regulation that students shall go to school on time. Students shall remain in the seats until all the papers have been collected.情态动词表义务（3）典例精析典例精析4. should表示“应该、必须”，通常表示自己的主观看法。例：The boys shouldnt be playing football. They should be at school.
3、We should protect our environment. 情态动词表义务（4）典例精析典例精析ought to表示义务，重于反映客观情况或涉及义务和规定，语气较should强。例：You ought to take care of the baby. You ought to be earning your living at your age. should与ought to1. My mother brings me up and takes good care of me, so when she is old I ought (look) after her in retu
4、rn. 解析：ought to表示义务，重于反映客观情况或涉及义务和规定。语法填空。语法填空。考点追击考点追击to look2. There was no more bus. They (have) to walk home. 解析：have to可用来表义务能用于多种时态。根据语境句子用一般过去时。had情态动词表可能和猜测语法精讲 概述情态动词中的must,can,could,may,might，will，would，should，ought to都表可能与猜测。用法用法1 11. 肯定句中一般用must (一定)，may (可能)，might / could (也许，或许)表可能和猜测。
5、例： Youre Toms good friend, so you must know what he likes best. Your mother may/might know the truth.1. 肯定句中表可能和猜测 用法用法2 2例：It cant/couldnt be the headmaster. He has gone to America. He may not/might not know the scientist. 2. 否定句中表可能和猜测 2. 否定句中用cant / couldnt(不可能)，may not/might not(可能不)表可能和猜测。用法用法3
6、 33. 疑问句中用can/could (能?)表示可能和猜测。例：Could he have finished the task? Can he be at home at present? 3. 疑问句中表可能和猜测 例：例：1.The clouds are gathering.Im afraid it might be pouring down soon. 2. The plane could be delayed by fog today.典例分析典例分析may和can的过去式？表示语气更加委婉或可能性较小4. should/ought to表可能和猜测时，意为“想必会，理应” 。用法
7、用法4 4例：Its seven oclock. Jack ought to/should be here at any moment. There shouldnt be any difficulty about getting you a visa. 4. should/ought to表可能和猜测 1. Peter may come with us last night, but he wasnt very sure then. 解析：may和might都可以表示可能和猜测，句子为过去时，要用过去式might。改错。改错。考点追击考点追击might2. It mustnt be his father. He has gone abroad.解析：mustnt表示“禁止”，cant表示“不可能”。cantBye-bye!
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