情态动词的推测性用法 1.Possibility(may/might/can/could) a.在疑问句中表示“可能”,须用can而不用may. b.在肯定陈述句中,用can表示“可能”与用may往往产生含义上的微妙差别:用表示“可能”往往指逻辑上的;用表事实上的。 Mr Reed is in poor health. He can be ill at any time. Mr Reed looks pale.He may be ill. c.用can表“可能”,较多地用于否定句和疑问句,could不受此限。 If you don't have a guide, you could lose your way. It cna't/couldn't be true. Can/Could the news be true? d.表过去的“可能”可用“may/might+不定式完成体或不定完成进行体”,也可用“can/could+不定式完成体”。 She may/might have been expressing her true feelings at that moment. She can't/couldn't have missed the train. e.用“might/could+不定式完成体”有式可以表本来可能发生但没有发生,或本来可能完成却没有完成的动作。 You might have killed yourself. I could have reported you.