[00:10.77]情态动词(Modal Verbs)
[00:19.50]情态动词表示说话人对某一动作或状态的态度
[00:26.18]情态动词本身有一定的意义，如must,can表示“必须,能够”，但不能单独作谓语
[00:38.67]比如我们不能说We must.He can.意义不完整
[00:45.51]要和动词原形一起连用，比如说，We must go.He can swim.
[00:55.95]情态动词没有人称和数的变化,比如说you must,I must,he must
[01:07.93]常用情态动词：can,could,may,might,must,have to,will,shall,would,should,
[01:27.78]need,dare,ought to等
[01:45.23]can和could
[01:50.54]1 表示“能力”，“允许”等，在口语中代替may,表示许可
[01:59.27]Ms Wang can drive acar now.(表示能力)You can go now.(表示许可)
[02:22.71]The teacher said wecould play footballafter school.(表示许可)
[02:49.06]2 could可以代替can,表示语气委婉
[02:53.75]Could you come herea little earliertomorrow?
[03:11.36]Could you help mewith my English?
[03:25.76]3 can与be able to两者都可以表示能力，
[03:25.76]can只能用于现在时和过去时中，其他时态则用be able to来表达
[03:51.03]Everybody can/isable to do that work.
[04:09.81]They haven't beenable to finishreading the books.
[04:36.62]I said I would beable to visit afterthe SARS.
[05:08.10] can与be able to
[05:12.38]要表达由于某人的能力和努力而成功地做成一些难做的事情时，用be able to
[05:24.07]They didn't agreewith me at first,but I was able topersuade them.
[05:53.76]He was a good runnerso he was able toescape from thepolice.
[06:26.75]4 表示推测，常用于否定句或疑问句中
[06:42.45]She's fat.She can'tbe a dancer.Can that man be ourteacher?
[07:37.81]Today is Sunday.Shecan't be working inthe office now.
[07:56.04]The ground is notwet at all.It can'thave rained lastnight.
[08:44.86]must和have to
[08:51.15]1 must表示“必须，应该”，否定形式表示“不准，禁止，不许可”
[09:06.66]The students mustobey the schoolrules.
[09:18.53]You mustn't playfootball in thestreet.
[09:36.02]Must we finish thework tomorrow?Yes,you must.No,you needn't
