语法：情态动词must和haveto.练习.doc

语法：情态动词must、have to 和have got to情态动词must和have to都有“必须”的含义，它们的用法如下：（一）、 must “必须”、“应该”的用法:1.must 表示“必须”、“应该”。例如：We must protect our environment.(我们必须保护环境。）Everyone must obey the rule.（人人必须遵守制度。）2. must的否定形式must not表示“不应该”、“禁止”、“不准”。语气比较强烈。例如：You mustnt speak like that.(你不应该像那样讲话。）You mustnt be late for school.（你不应该上学迟到。）3.在回答must的问句时，肯定形式用must来回答，但否定形式用neednt 或dont have to来回答。而不用mustnt来回答。例如：Must I be home before 8 oclock?(8点之前我必须回家吗？) Yes, you must. No, you neednt./No, you dont have to. （是，你必须。） （不，你不必。）4.must还可表示推测，意思是“一定”、“必定”，一般只用于肯定句中。分三种情况：1.）对于现在状态的推测，我们用：must +v.（状态动词或系动词），例如：He must be at home.(他准在家里。）There must be some children in the room.（房间里准有些孩子。）2.）对于现在动作的推测，我们用：must +be + doing（行为动词），例如：They must be cleaning their room.(他们准是在打扫房间。）He must be watching TV.（他准是在看电视。）3.）对于过去事实的推测，我们用：must +have +过去分词，例如:It must have rained last night.(昨晚准是下雨了。）I didnt hear the phone. I must have been asleep.（我没有听到电话，我准是睡着了。）（二）、have to 表示“必须”、“不得不”，例如：He has to stay in bed for 3 or 4 days.(他必须卧床休息三四天。）We will have to get up early tomorrow.（明天我们必须早起。）（三）、have got to是 have to的口语形式。例如： Ive got to leave for Nanjing.(我不得不去南京。)*Must与 have to的区别： must表示的是说话人的主观看法，而have to则表示的是客观需要。Must一般只有现在时，而have to有更多的形式。I must go now.(主观看法) My mother is ill, so I have to go now.(客观需要)*Have to与 have got to的区别： have got to虽然是have to的口语形式，但二者在用法上有严格的区别： have to的前面还可以用情态动词或助动词，而have got to却不可以； have to的否定形式为dont/doesnt /didnt +have to,疑问式为Do/Does/Did + 主语 + have to?而 have got to的否定形式是在have后加 not,疑问式把have提前。例如： We dont have to go home. Do you have to go home? We havent got to go home. Have you got to go home?练习：一、.Fill in the blanks using have to, have got to, must, should, ought to, had better.1.You _ not get down until the bus has stopped.2.They _ be encouraged to speak English after class.3.You often _ wait a long time for a bus.4.We _ go and see Mary tomorrow, but I dont think we will.5.I _ not miss my train.6.When traveling, you _ take care of your health.7.In some parts of the world, you _ boil the water before drinking it.8.If you have a stomach pain, you _ drink hot weak tea.9.You _ not swim immediately after a heave meal.10.You _ not wake me up when you come in.11.He _ be ill, for he looks so pale.12.You _ not have given him the money.13.Its getting late. I am afraid I _ go.二、Choose the best answer.1.-Must I do it now?-No, you _. A. neednt B. dont have to C. mustnt D. A or B2.Its nearly seven oclock. Jack _be here at any time. A. must B. need C should D can.3.-When can I come for these photos? I need them tomorrow afternoon.-They _be ready by 12:00. A. can B. should C. might D. need4.Sorry, Im late. I _ have turned off the alarm oclock and gone back to sleep again. A. might B. should C. can D. will5.I told Sally how to get there, but perhaps I _ for her. A. had to write it out B. must have written it out C. should have written it out D. ought to write it out6.Jenny _ have kept her word. I wonder why she changed her mind. A. must B. should C. need D. would7.Tom ought not to _ me your secret, but he meant no harm. A. have told B. tell C. be telling D. having told8.Sir, you _ be sitting in the waiting room. It is for women and children only. A. oughtnt to B. cant be C. wont D. neednt9.If you really want yourself to be in good health, you must _always _ so much. A. not, be smoking B. not, have smoked C. not, to smoke D. be not, smoking10.I didnt hear the phone, I _ asleep. A. must be B. must have been C. should be D. should have been11.I was really anxious about you. You _ home without a word. A. mustnt leave B. shouldnt have left C. couldnt have left D. neednt leave12.Youd better go at once, _ you?A. shouldnt B. wouldnt C. hadnt D. couldnt13.She ought to be praised, _? A. ought she B. she ought C. oughtnt she D. she oughtnt14.He _ go there by train. A. oughtnt to B. oughtnt C. ought to not D. didnt ought to15.-Look, it_ be Mr. Wang. -No, it _ be him. He has gone abroad. A. may; mustnt B. must; may not C. must; cant D. can; may not三、Correct the mistake in each se