Modal Verbs情态动词( ) 情态动词(2)表示推测的用法

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2010 TEM4Nancy's gone to work but her car's still there. She ____ by bus. A. must have gone √ B. should have gone C. ought to have gone D. could have gone

2009 TEM4She _____ fifty or so when I first met her at a conference. A. had been B. must be C. has been D. √ must have been

Modal verbs and their negativespositive must (used for a personal opinion) He must be crazy. must / have to / has to (used for obligation)You must arrive by 8 o'clock. You have to arrive by 8 o'clock.

negative can't He can't be crazy.don't have to / needn't = something is not necessary You don't have to arrive by 8 o'clock. You needn't arrive by 8 o'clock.

Modal verbs and their negatives

positive can (used for ability) I can play the guitar. can (used for possibility) You can smoke here.

negative can't / cannot I can't play the guitar. can't / cannot / mustn't You can't smoke here. You mustn't smoke here.

MODAL VERBS: POSSIBILITYThere are several modal verbs used to show possibility. They are Might, May, Could, and Must. All of these are different ways to say maybe. Modal Verb + Base Verb

I may eat dinner at 7:00pm. She might work late tonight. They must be tired.

MODAL VERBS: POSSIBILITYCould and might express remoteness of any kind (past time, unlikely occurrence, stiffness due to shyness or respect-.. ) May and might express a more personal involvement in the creation of the possibility (an extrictly personal opinion, or some kind of authority..)

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MODAL VERBS: POSSIBILITYThere are many kinds of possibility: Probability, chances: This could be your lucky day (It is likely, possible that..) Theoretical possibility, options: We can be friends, if you want to. Ability: He can dance on his nose (He is able to..) Assumptions (logical possibility): This may well be the purse you lost Permission: Can I go to the cinema? –No, you may not. (You’re not allowed to..)

Perfect modals of possibilityOne of the most common uses of perfect modals of possibility is for assumptions about the past: we look back on an action that happened before, but we consider it now. That is how we can discuss the possibility of past facts now, or make regrets: It could have been a great opportunity. You could have been a bit more talkative!

CompareIt could be a terrific day for Man U.. (Now we think there is a remote chance that it will be a terrific day) It could have been a terrific day... (We now think that it was possible before that it was a terrific day . We assume that it is impossible now).

CompareHe might have been trapped in the mud. (We now think so) He might be trapped in the mud. (action now, possibility now as well) They might be the winners. (present winners) They might have been the winners. (we think so now, but this sentence sometimes suggests they weren’t).

Could"Could" is used to express possibility or past ability a

s well as to make suggestions and requests. "Could" is also commonly used in conditional sentences as the conditional form of "can." Examples: Extreme rain could cause the river to flood the city. (possibility) Nancy could ski like a pro by the age of 11. (past ability)

"Could not" vs. "Might not""Could not" suggests that it is impossible for something to happen. "Might not" suggests you do not know if something happens. Examples: Jack might not have the key. (Maybe he does not have the key.) Jack could not have the key.(It is impossible that he has the key.)