表推测时，英语中只使用must,may,might,may not和can't。这五个表达的语气依次递减： must:一定（语气肯定） may：也许（不很肯定） might：或许（比may语气更弱） may not：也许不（表否定） can't：一定不（must的反义） 推测现在的事情用must,may,might,may not和can't+do或be e.g.She must be at home now. The boy may play now. 推测过去的事情用must,may,might,may not和can't+have done e.g.She might have been ill yesterday. He must have hold the party. 注意：表推测的must,may,might,may not和can't是不可以与I think...连用。因为I think...已有推测的含义，故不能连用