Use some modal verbs to say sth. that is possible.MUSTCANMIGHTFORMS 肯定形式 否定形式 疑问形式 备注 must / / can can’t/cannot Can··· ？ could could not Could··· ？ may may not might might not COULDMAY ORDER:Might May Could Can MustUNCERTAIN CERTAIN( 可能是 Kate 。 )( 绝对不是 Marry 。 )( 可能不是 Tommy 。 ) Mum: Who is it? Jim: ( 一定是 Tom 。 )It must be Tom.It may be Kate.It can’t be MarryIt couldn’t be Tommy. mustcan / couldmay / mightWhen you are very sure of something, you use must in positive sentence and cannot or can’t in negative sentences.When you are quite sure about something, you use can.When you think that something is possible, but you are not very sure, you use could, may or might.2. It must have rained last night, _________?1. It must be nice to take a walk here, __________?1. must 表示推测时，其反意疑问句应根据动词的实际时态而变化。如： isn’t it didn’t itWe must have been met somewhere before.You must have seen her yesterday, didn’t you?2. Must have done 意为“一定做过”，表示对过去发生的事情进行肯定推测。如：1. 我们以前一定在哪里见过面。2. 你昨天一定看到她了，对不？1. can / could 表示的可能性比 must 小， can 表现在和将来， could 既可表过去，也可表现在或将来，但它的可能性比 can 小。2. can / could 可与 not 连用，表示否定推测，也可用于疑问句中 .3. Can / could 表推测时，其反间疑句也是根据动词的实际时态国以变化。如：你不可能当真的，对不对？You can’t be serious, are you?4. can / could have done ，意为“本来能够”，用于否定句时，意为“过去（不）可能”，而实际上都未发生。 如： 你本来可以来早点的。You could have come earlier. 1. may / might 的可能性最小，往往表示原因说话人对某事没把握2. May / might 可与 not 连用，表示否定推测，但 may 用于疑问句时中能表示请求允许。The teacher may not be serious.May I leave now?3. May...
