1、Unit 4 Road safety 情态动词 情态动词 can, could, may, might, will, would, shall, should, must和ought称为情态动词。它们和 主要谓语动词一起构成谓语。绝大多数情态 动词的意思可以划分为两类。 一类是表示可能性：情态动词可以用来表示某种 情况是肯定的、或很可能的、或可能的、或不 可能的。 另一类意思涉及必须做某事或允许做某 事之类的意思：情态动词可以用来表示 某人必须做某事、某人能做某事，如果 某事发生（或不发生）就会好一些，或 者某事是许可或禁止的。 a完全有把握(肯定的或否定的） 1.shall用于第一人称： I
2、/We shall be away tomorrow. I shant be late on Wednesday. 2. will 用于各种人称： Thats the phone. Thatll be Tony. Things will be right. It wont rain this evening. Youll be right. 3. must只用于肯定句中： He decided Franklin must be suffering from a bad cold. 4. cant和couldnt表示现在或将来不可能， couldnt用于间接引语中，表示过去不可能： 1)That
3、 cant be Mr. Smithhes in New York. 2)I knew it couldnt be Mr. Smith. 3)He couldnt be at home. 5. would, wouldnt 用于间接引语中，表示过 去可能或不可能： I told you wouldnt be ready in time. 1. should, shouldnt, ought to, oughtnt to, may well (很有可能）, may, may not （可能、可 能不） : 1)She should/ought to be here soon. 2)It shou
4、ldnt/oughtnt to be difficult for you to work out the problem. 3)We may be buying a new flat. 4)The list may not be complete. 5)“I think its going to rain.” “You may well be rightthe sky is really black. b很有可能/可能 C可能性小 might, mightnt, could,它们不是may, can的过 去式，它们都可以用来谈论现在和将来, could比may 和might更不可能： 1)I
5、might see you againwho knows? 2)Things might not be as bad as they seem. 3)We could all be millionaires one day. 的的 特点特点 1）有特定的词义）有特定的词义 2）没有人称和数的变化）没有人称和数的变化 3）其后加动词原形）其后加动词原形(do), have done ,be doing. 情态动词情态动词 情态动词情态动词 1。区别。区别must / have to Must表示人在主观上认为的必要、必须、一定要表示人在主观上认为的必要、必须、一定要 Have to表示受环境或习
6、惯支配的客观必要表示受环境或习惯支配的客观必要 “不得不”，能用于更多时态。“不得不”，能用于更多时态。 1)Soldiers _obey officers. 2)Its raining outside.We_stay at home. 3As he had broken his leg, he _lie in bed. 易混易错用的情态动词易混易错用的情态动词 must have to had to 2。表示能力。表示能力: can, could, be able to *be able to 能用于能用于各种时态各种时态。 can / could 只能表示只能表示现在现在或或过去过去的能力
7、。的能力。 *was / were able to : “设法做成某事”设法做成某事” 相当于相当于 managed to do sth. succeeded in doing sth.。 Eg.Though they were trapped in the big fire, they _escape. were able to 3。can (用于疑问句中）， cant, could, may, might, should, ought to, will, must + have + 过分可以表示对过去发生的事情作出推断： 1. Where can he have gone? 2. We c
8、ant have taken it upstairs this morning! 3. I may / might/ could have come to a wrong conclusion. 4. That was a bad place to go skiing. You might have broken your leg. 二、表示必须和允许做某事二、表示必须和允许做某事 情态动词可表示必须和允许做某事的各种含义。情态动词可表示必须和允许做某事的各种含义。 情态动词的这类用法很重要，可以有礼貌地情态动词的这类用法很重要，可以有礼貌地 表达请求、建议、邀请和批示。表达请求、建议、邀请和
9、批示。 a must, will, need (用于疑问句中）强调必用于疑问句中）强调必 要性；要性；shall(用于二、三人称表示说话人 的意愿、承诺、命令或法律、规章、制 度上要求必须做的事情） ： 1. Teachers of English must be in the classroom by 7.10. 2. All sales staff will arrive for work by 9.00. 3. Need I get a visa for Hong Kong? 4. You shall have the book as soon as I finish it. 5. He
10、 shant come here. 6. He shant pass the math exam. 7. A record shall be kept of the number of students attending each class. 8. “Can someone help me?” “I will.” 9. Ill definitely pay you back next week. 10. Ill kill her for this, Sue said. 11. “Give me a kiss.” “No, I wont.” 12. The car wont start. w
11、ould指过去愿意；wouldnt指过去拒绝： 1. My husband would do the dishes, but he wouldnt cook. 2. I asked him politely, but he wouldnt tell me. 3. The car wouldnt start this morning. 1. You mustnt drive fast. Theres a speed limit. 2. Magazines may not be taken out of the library. 3. You cant come in here without p
12、ermission. c 禁止 mustnt, may not, cant 可以表示 禁止，may not非常正式，在非正式文体 中cant更常见；mustnt比may not 更为 强调： 其他意思： 1. must 可以表示偏要： If you must drink so much, of course youll feel sick. Naturally, after I gave her my advice, she must do the opposite. 2. will可以表示常常，would可以表示过 去习惯性的行为。used to用来谈论习惯 性行为或习惯性状态，而would只可谈论 习惯性行为:
