1. 肯定的推测一般用must, should, may（might）或could（不用can），其中，must的语气最强，译为“肯定”、“准是”、“想必是”；should的语气次之，译为“很可能”、“应该”，指按常理推测；may（might），could的语气最弱，译为“也许”、“可能”。Helen _ go on the trip with us but she isnt quite sure yet. A. shall B. must C. may D. canIve taken someone elses green sweater by mistake.It _ Harrys. He always wears green. A. has to be B. will be C. mustnt be D. could beI have lost one of my gloves. I _ it somewhere.A. must drop B. must have droppedC. must be dropping D. must have been droppedIf I _ plan to do anything I wanted to ,Id like to go to Tibet and travel through as much of it as possible. A. would B. could C. had to D. ought to2. 否定推测分为两种情况：1）语气不很肯定时，常用may not, might not或could not，译为“可能不”、“也许不”。You might just as well tell the manufacturer that male customers _ not like the design of the furniture. （2004年上海春季卷）A. must B. shall C. may D. need2）否定语气较强时，则用cant，译为“根本不可能”、“想必不会”，表示惊异、怀疑的感情色彩。Do you know where David is? I couldnt find him anywhere.Well. He _ have gone farhis coats still here.A. shouldnt B. mustnt C. cant D. wouldnt Isnt that Anns husband over there? No, it _ be him Im sure he doesnt wear glasses. A. cant B. must not C. wont D. may not3. 疑问句中的推测，往往用can或could。Mr. Bush is on time for everything. How _ it be that he was late for the opening ceremony？（2001年上海春季卷）A. can B. should C. may D. must4. 对已发生事情的肯定推测常用“must, may, might等+完成式”；否定推测常用“can, could, may, might等+完成式”。I was on the highway when this car went past followed by a police car. They _ at least 150 kilometers an hour.A. should have been doing B. must have been doingC. could have done D. would have doneHe _ have completed his work; otherwise, he wouldnt be enjoying himself by seaside. （2005年北京卷）A. should B. must C. wouldnt D. cantTom is never late for work. Why is be absent today?Something _ to him. A. must happen B. should have happenedC. could have happened D. must have happened My sister met him at the Grand Theatre yesterday afternoon, so he_ have attended your lecture.（2000年上海卷）A. couldnt B. neednt C. mustnt D. shouldnt二、“情态动词+完成式”1. “should（ought to）+完成式”表示本应该做某事而实际上没有做。其否定式表示某种行为不该发生但却发生了。Ill tell Mary about her new job tomorrow. You_ her last week. A ought to tell B would have toldC must tell D should have toldOh, Im not feeling well in the stomach, I _ so much fried chicken just now. A. shouldnt eat B. mustnt have eatenC. shouldnt have eaten D. mustnt eat2. “could+完成式”表示本来能够做成某事的但结果没能做成，含有遗憾的意味。He paid for a seat, when he _ have entered free. A. could B. would C. must D. need3. “neednt+不定式的完成式”表示本来不必做某事而实际上做了某事。例如：You neednt have watered the flowers, for it is going to rain.你本不需要浇花的，因为天就要下雨了。 Catherine, I have cleaned the room for you. Thanks. You _ it. I could manage it myself. A. neednt do B. neednt have done C. mustnt do D. shouldnt have done三、常见的情态动词1. shall用于一、三人称疑问句表示征求对方意见；用于二、三人称陈述句表示说话人给对方的命令、警告、允诺或威胁等。“The interest be divided into five parts, according to the agreement made by both sides，” declared the judge. A. may B. should C. must D. shallExcuse me, but I want to use your computer to type a report. You _ have my computer if you dont take care of it. A. shant B. might not C. neednt D. shouldnt The room is so dirty. _ we clean it? Of course. A. Will B. Shall C. Would D. Do2. must用于疑问句，表示责备、抱怨的感情色彩，意思为“偏偏，偏要”；mustnt表示禁止，是说话人强有力的劝告。John, look at the time. _ you play the piano at such a late hour？ A. Must B. Can C. May D. NeedTom, you leave all your clothes on the floor like this！A. wouldntB. mustntC. needntD. may not3. neednt表示“没有必要”。 Lucy doesnt mind lending you her dictionary. She _. Ive already borrowed one. A. cant B. mustnt C. neednt D. shouldnt4. would表示过去反复发生的动作或某种倾向。When he was there, he _ go to that coffee shop at the corner after work every day.A. would B. should C. had better D. might5. 表示经过努力而成功的某一次动作，只能用was/were able to，而不能用could。The fire spread through the hotel very quickly but everyone _ get out. A. had to B. would C. was able to D. could6. 考查情态动词用作答语的情况Write to me when you get home. _. A. I must B. I should C. I will D. I can Could I call you b