情态动词是一种本身有一定的词义，表示说话人的情绪，态度或语气的动词，但不能单独作谓语，只能和其他动词原形构成谓语。下面让我们看一下情态动词表推测的三种时态
1．对将来情况的推测，用“情态动词 + 动词原形”。
例句1：(1)．She must / may / might / could arrive before 5.5:00前她一定/可能/也许到。
例句2：She must/may/might/could walk miles and miles among the hills without meeting anyone.她一定/可能/也许会在山里一连走好几英里而遇不到一个人。
2．对现在或一般情况的推测，用“情态动词 + be”，“情态动词 +be doing”或“情态动词 + 动词原形”。
例句1：He must / may / might / could be listening to the radio now.他一定/可能/也许正在听收音机。
例句2：Mr. Bush is on time for everything .How can ( could ) he be late for the opening ceremony.布什先生一向准时，这次开幕式他怎么可能迟到呢？
3．对过去情况的推测，用“情态动词 + have +过去分词”。
例句1：It must / may / might / could have rained last night .The ground is wet.地湿了，昨晚肯定/可能/也许下雨了。
例句2：The door was locked. He can ( could ) not / may ( might ) not have been at home .门锁着，他不可能/可能不在家。
