[00:13.51]2 must表示推测，用于肯定句中They must be tiredafter the long trip.
[00:41.43]The lights is stillon in his room.He must be studyingnow.
[01:06.77]The classroom is soclean.The studentsmust have cleanedit yesterday.
[01:49.73]3 have to表示“必须，不得不”，可用于多种时态
[02:01.36]They have to leavenow.He has to walk toschool every day.
[02:12.94]You don't have tofinish the soup ifyou don't like it.
[02:42.58]She missed the bus,so she had to takea taxi.
[03:05.07]I'm sorry I won't goshopping with younext week. I'll haveto visit my teacher.
[03:34.07]4 have to和mustYou don't have totell him the news.
[03:56.63]You mustn't tell himthe news.
[04:30.72]We must clean ourclassroom every day.(作为一种义务，无论干净与否，每天要扫)
[04:48.11]I have to leave now.It's getting late.(天黑了，不允许我再呆下去了)
[05:22.32]1 may表示允许或征询对方许可You may go out andplay football.
[05:35.00]May/Might I watch TVafter I finish myhomework?
[05:56.72]May I smoke in theroom?__Yes,you may./__Yes,please.
[06:12.33]__No,you mustn't.__No,you can't.__No,you'd better not.
[06:46.34]The foreign friendsmay come tomorrow.It might snow thisevening.
[07:40.72]May you have a goodtrip.May you succeed.
[08:07.26]He needn't buy thatbook.
[08:27.30]Need he go at once?__Yes,he must.__No, he needn't
[09:03.88]2 dare作为情态动词主要用于否定和疑问句中How dare you saythat?
[09:23.00]She dare not ask herdad for money.
[09:39.15]3 need和dare也可以用作实意动词，其变化与一般动词相同。内容来自 听力课堂网：http://www.tingclass.net/show-9967-388243-1.html