1、表示推测情态动词的用法表示推测情态动词的用法 一、用法归纳1. 表示推测的情态动词有 must, can, could, may, might 等，且语气由左向右依次减弱。could, might 并不一定是 can, may 的过去式，有时只是语气分别比 can, may 更弱。2. must (一定会，准会) 只用于肯定句；can (可能) 一般用于疑问句或否定句；may (也许) 用于肯定句或否定句。虽然 must 和 may 均可用于肯定句，但在语气上 must 比 may 强得多，must 表示有把握的肯定推测，而 may 表示没有把握的肯定推测。虽然 can 和 may 均可用于否
2、定句，但在语气上 cant(不可能)比 may not(可能不)要强得多，cant 是表示有把握的否定推测，而 may not 是表示没有把握的否定推测。could, might 可用于肯定句、否定句或疑问句中，其区别在于语气上强弱的区分。3. should, ought to (按理应当 ), would, will,(很可能) 等也可表示推测，语气都较肯定，且由左至右依次增强，但较 must 稍弱。4. 关于表示推测的情态动词后面所接动词形式，有下列三种情况：若对此刻正在发生的事，接“be +现在分词”；若对现在或未来情况的推测，接动词原形；若对过去情况的推测，接“have +过去分词”。
3、二、实例分析Excuse me. Is this the right way to the Summer Palace?Sorry, I am not sure. It _ be. (湖北卷)A. mightB. willC. must D. can【分析】答案选 A。由 I am not sure(我没有把握) 可知，后文是没有把握的肯定推测，用might。 You might just as well tell the manufacturer that male customers _ not like the design of the furniture. (上海卷)A. mustB
4、. shall C. mayD. need 【分析】答案选 C。. may not 意为“ 可能不”。句意是：你不妨告诉厂商男顾客可能不喜欢这种家具的花样。 Isnt that Anns husband over there? No, it _ be himIm sure he doesnt wear glasses. (全国卷)A. cant B. must not C. wontD. may not【分析】答案选 A。由 No 和后文 Im sure可知，是有把握的否定推测，所以用 cant (不可能)。When can I come for the photos? I need them
5、 tomorrow afternoon. They _ be ready by 12:00. (全国卷)A. can B. shouldC. might D. need【分析 】答案选 B。should 表示“按理应当，大概” 。用 might 语气太不肯定，顾客可能走掉。I have lost one of my gloves. I _ somewhere. (北京春)A. must dropB. must have droppedC. must be dropping D. must have been dropped【分析】答案选 B。对已经发生的事进行推测用 “must have +过
6、去分词” ，答案 D 是被动式，应排除。I stayed at a hotel while in New York. Oh, did you? You _ with Barbara. (全国卷)A. could have stayedB. could stayC. would stayD. must have stayed 【分析】答案选 A。表示对过去情况的推测：“你可能和 Barbara 住在一起了”；must 语气太肯定，与前面具有疑问语气的 Oh, did you?不符。There were already five people in the car but they managed
7、 to take me as well. It _ a comfortable journey. (全国卷)A. cant beB. shouldnt beC. mustnt have beenD. couldnt have been【分析 】答案选 D。既然小汽车上 “已有五人”，且是“ 设法” 才把你带去的，如此拥挤，旅途当然“不可能” 舒服。Tom graduated from college at a very young age. Oh, he _ have been a very smart boy then. (全国 III)A. couldB. shouldC. mightD.
8、 must【分析】答案选 D。由上文可知，应是有把握的肯定推测，用 must(一定)。You _ be tiredyouve only been working for an hour. (四川卷)A. must notB. wontC. cantD. may not【分析 】答案选 C。由后文 “你才只工作了一个小时”推断， “你不可能就累了” 。表示有把握的否定推测，用 cant。must not 不允许；may not 可能不。Its nearly seven oclock. Jack _ be here at any moment. (全国卷)A. must B. needC. sho
9、uldD. can【分析】答案选 C。nearly 暗示“ 时间不早了”， “按理应当 (should)”Jack“随时(at any moment)”都有可能到达这里。must 又语气过强；can 一般不用于肯定推测； need 意义不通，也不用于肯定句。I didnt hear the phone. I _ asleep. (全国卷)A. must be B. must have beenC. should beD. should have been【分析 】答案选 B。当时我没不听到电话铃响，那“一定是己经睡着了。Is John coming by train?He should, bu
10、t he _ not. He likes driving his car. (全国卷)A. mustB. canC. needD. may【分析】答案选 D。由“他自己喜欢开车 ”这一习惯推断， “他可能不会(may not)坐火车来”。can not“不可能” ，语气太肯定。(from )Peter _ come with us tonight, but he isnt very sure yet. (全国卷)A. must B. canC. mayD. will【分析】答案选 C。由 but he isnt very sure. (但他没有把握)可知，Peter 晚上来的可能性是不大的。表
11、示没有把握的肯定推测用 may(也许)。Are you coming to Jeffs party?Im not sure. I _ go to the concert instead. (全国卷)A. mustB. wouldC. should D. might【分析 】答案选 D。由 Im not sure 可知， “我可能(might)要去听音乐会”Michael _ be a policeman, for hes much too short. (上海卷)A. needntB. cantC. shouldD. may【分析】答案选 B。由 hes too short 推知，Michael“不可能(cant)”是 policeman。
