(一)表示推测的情态动词
对现在或将来情况推测,用情态动词+do / be / be doing…;对过去的推测,用情态动词+have done / been…;表示肯定推测的情态动词按可能性大小依次为 must, should / ought to, may, might, could;否定推测,常用can’t
/ couldn’t,译为“根本不可能”、“想必不会”,表示推测的语气非常肯定,may not, might not或could not译为“可能不”、“也许不”,表示推测的语气不很肯定。
(1)
must表示推测,意为“一定……”,只能用于肯定句中。 must have done意为:一定做过某事或某事肯定发生了。
例如:
(NMET2007 江苏)-She looks very happy. She ______ have passed the exam.
-I guess so. It’s not difficult after all.
A. should B.
could
C. must D. might
[解析]句意为:她看上去很高兴,一定是通过了考试。
[答案]C
(2)
should (not) / ought (not) to在中表示根据常规或常识推测,表示“某事应该或不应该发生”,语气比must或can’t / couldn’t稍弱。
例如: (NMET2007全国I)-How’s your tour around the North Lake? Is it beautiful?
-It ________ be, but it is now heavily polluted.
A. will B.
would C. should D. must
[解析]should此处表示推测,意为“应该”。
[答案]C
②(NMET2005上海)There _________ be any difficulty about passing the road test since
you have practiced a lot in the driving school.
A. mustn’t B. shan’t C. shouldn’t D. needn’t
[解析]句意:既然你在驾校进行了大量训练,那么通过道路测试按理不应该有困难。
[答案]C
(3)
can, could表达推测时,一般用于疑问句和否定句中;can用于肯定句中表示一种理论上的可能性,并不牵涉是否真的会发生,在这种用法中can只能与动词原形连用;could用于肯定句中,语气比may/ might更弱。例如:
①(NMET2008浙江)You
______ be hungry already - you had lunch only two hours ago!
A. wouldn’t B.
can’t C. mustn’t D. needn’t
②(NMET2008天津)She
______ have left school, for her bike is still here.
A. can’t
B. wouldn’t
C. shouldn’t D.
needn’t
③(NMET2008福建)It
is usually warm in my hometown in March, but it _____ be rather cold sometime.
A. must B. can C. should
D. would
④(NMET2008辽宁)Peter
____ be really difficult at times even though he’s a nice person in general.
A. shall B.
should C.
can D.
must
[解析]①② 两个考题中can用于中表示否定的推测,意为:不可能,一定不会;
③④两个考题中can表示理论上的可能性,翻译为:有时候会……。
[答案]① B ② A ③ B ④ C
(4)may (not) / might (not)表达一种不太把握的推测,意为“或许,可能”;might的语气比may较婉转。例如:
① (NMET2008全国II) Liza ___ well not want to go on the trip --- she hates
traveling.
A. will B. can C. must D. may
[解析]may well为固定搭配,意为:很可能,极有可能。
[答案]D
② (NMET2008四川) Although this ____ sound like a simple task, great care is needed.
A. must B. may C. shall D. should
[解析]这听起来或许是一项简单的任务,但却需要极大的细心。
[答案]B
③ (NMET2008重庆)-I can’t find my purse anywhere.
-You __ have lost it while shopping.
A. may B. can C. should D. would
[解析]结合语境可知,回答者是在提醒对方:或许购物时把钱包丢了。
[答案]A