情态动词表推测课件.ppt

ModalVerbs
情态动词 can, could, may,might,must表推测的用法:
情态动词中的can, could, may, might, must都表推测。其中must的可能性最大,can / could次之,may / might最小。具体用法如下:1. must的用法(1)表示推测“可能性”时,意思是“一定、准是”,语气较肯定,较有把握。He must be American. = It is certain that he is American. 他准是个美国人。
(2)must表推测只能用于肯定句。
如表示“一定不、肯定不”的意思时,应用can`t,
如询问某种可能时,应用can。He must know my address. 他肯定知道我的地址。
(一定) He can`t know my address. 他肯定不知道我的地址。
(一定不)Can he know my address? 他知道我的地址吗?
(询问可能性)
(3)must表示推测时,可以推测现在/正在发生的动作/过去发生的动作。He must have a car now. (现在)他一定有辆小汽车。He must be doing his exercises in the classroom.(正在进行)他一定在教室里做练习。He must have finished the work.(过去发生)他一定已完成了工作。注:must表示推测时很少用于将来的情况。一般不用He e `s certain / I`m sure that he e tomorrow.
(4)在反意疑问句中,当附属部分含有表示推测意义的must时,疑问部分的助动词应与must后面的动词在非推测情况下的用法保持一致。He must be a worker, isn`t he? (现在)他准时个工人,是吗?
You must have learned English for many years, haven`t you? (完成时)你一定学了好多年英语,是吗?比较:
It must have rained last night, didn`t it? (过去)昨晚一定下雨了,是不是?He must have arrived by yesterday morning, hadn’t he?
2. can / could的用法(1)can表示推测“可能性”时,往往用于否定句或疑问句。Can`t“一定不”,can在疑问句中意思是“会、可能”。He can`t be at home. = It is impossible that he is at home. 他一定不在家。(2)can /can`t+ have done,表示对过去发生的动作进行推测。He can`t have gone to Shanghai for I saw him a minute ago. 他不可能去了上海,我刚才还看见他。It`s so late. Where can she have gone? 天晚了,她可能去哪儿了呢?
(3)could 还可以用于表示客气、委婉、礼貌的请求语气。
Excuse me, could you tell me the way to the bus station?Could you help me?
(4)could have done
本能做但未做,表虚拟语气
I could have done it well,but I wasn’t so careful then .
3. may和might的用法(1) may, might表示推测“可能性”时,意思是“可能”、“也许”He may / might be American. = It is possible that he is American.他可能是个美国人。注:might不表示过去时态,只是语气上比may更委婉,表示的可能性更小。(2)may, might表推测时,可以用于否定句,意思是“可能不、也许不”,但不用于疑问句。He may / might not be at home. 他也许不在家。
(3)may, might可以推测现在正在发生的动作或过去发生的动作。He may / might be sleeping now.
The boy may / might not be watching TV at home.  这个男孩可能没在家看电视These students may / might have seen the film
before.(过去) 这