辨析must-和-have-to詳解和練習

1、Must 和 Have tomust （無詞形變化）（1）。 表"必須"，"應該"， "務必 " must not（mustn't） 表 "禁止"，"不許"，"不準"，"不可以"。Everyone mustattend the lecture. The work must be finished as soon as possible.You mustn't lend it to others.注；對 must 問句的回答。-Must I

2、go there now?-Yes, you must.-No ,you needn't. need not don't have（got） to don't need to.2.must 表推測 "一定"， "必定 "，一般只用于肯定句，亦即用于疑問句和否定不表揣測。（ 1 ）對現(xiàn)在He must be at home now. You must be hungry after the long walk.The Chinese language must have the largest number of speakers.

3、2 2） 對進行時。He must be sleeping now（at that time）.（ 3）對過去時或完成時。It must have rained last night. He must have fallen asleep（then）.He must have gone to Beijing yesterday. She must have been young when she got married .注意其反意問句。3 .must 表不可避免的傾向。All men must die.4 . must 表 "偏偏" ， "不巧 " M

4、y car must break down. 我的車偏偏壞了。have to " 不得不 "1 . 與 must 的區(qū)別 （ 1） must 表說話人的主觀看法，而have to 表客觀需要。比較： I have to stop smoking .（ 外界壓力，客觀情況使然）I must stop smoking. （主觀認為）2 .must 只有一種形式而have to 有更多的形式have to, has to ,had to ,will have to 等等。I thought I must go there.3 .have to 的疑問，否定均須借助于do。Does

5、 he have to go there now ?不說 Has he to go there now?He has to go there now, doesn t he? The work has to be finished before 10 o'clock.4 .must 與 had to 的差別：had to 還可以表示業(yè)已完成或?qū)崿F(xiàn)的動作（即；動作確實做了）。I had to stay at home last night.Can1 .表 " 能力 "I can lift the stone. I can speak English while he

6、can't. Who can play the violin? He got up early yesterday so that he could catch the early bus.could 表過去的能力。注； 1。 can 與 be able to 表能力時的區(qū)別： 形式上；can有兩種形式can與could ,而be able to有更多的形式。is(are)able to, was able to , has been able , will be able to , would be able to 等。be able to 只表能力而can 還可表"可能性

7、"， "驚異 ","許可 "等。 could 與 was able to 表過去能力的差別：均表過去的能力，但was( were) able to 還可表業(yè)已成功的行為(即：動作確實做了)。2表" 許可 "You can go now. You can use my dictionary. You can have a rest.-Can I smoke here?-No, you can't.注：用 could 代替 can 在疑問句中，語氣客氣委婉，但在時間上還指現(xiàn)在.Could you lend me your

8、 bike?Could you tell me how to get to the station?注意：回答由could 引起的問句，仍用can 而不用 could。-Could you wait a few more minutes?-Yes, I can.3.表猜測"可能"，一般用于疑問句和否定句。-Can the news be true? -It can't be true. Where can he be?注： (1)can't 表 "不可能"，語氣斷然否定。(2) could 在賓語從句中表過去的可能性，其它情況一般還表示現(xiàn)

9、在的可能性只是語氣比can 委婉和更加不肯定。I thought he could come .(3) can 亦可用于肯定句表可能，但表示的是邏輯推理上的可能性(或理論上的)， 非主觀臆斷。There canbe no noise on the moon because of sound being carried by the air .(4) can(could) have donecan(could) have been(doine斤疑問句或疑問句表對過去時或完成時的揣測。What can have happened to him ? He can not have read the

10、book. He can't have been to Beijing.(5) " 驚異 "" 驚訝 "： How can you be so impolite? How can you say that?May表 " 允許 "" 許可 "" 允諾 "(征詢對方許可)。You may go now . May I use your bike? You may keep the book for 2 weeks . 注意：(1)其否定形式 may not表示不可以，但更常用must not

11、來代替may not表示"不可以"，"禁止"。-MayI watch TV after supper?-Yes, you may.(No, you mustn't . 或 No, you may not. 或 No, you'd better not.)(2)與 can 的比較： may 比 can 更正式。 May I know your name? May I (he, we).?x May you .？ (May you have a good journey!止匕處表祝愿)( 3) 。 might 代替 may 用于疑問句，更客氣

12、禮貌些，回答時仍用may。-Might I use your telephone? -Yes, you may .(4)might not 不表示 " 不允許 "2.表"可能"。(1)用于肯定句和否定句(因為 May I彼征詢許可)。The news may be true . He may not be at home now. I think he may come today(tomorrow).However fast you may run, you can't catch the fast train.(2)用might語氣更加不肯定

13、，但指現(xiàn)在或?qū)?，只有在賓語從句中might do (be)才表示過去可能性。He might come today(tomorrow). She might have some fever .I thought you might like something to read, so I brought some books for you .She said she might not be at home. I might be busy tomorrow.(3)may not 與 cannot 的區(qū)別：may not"可能不", cannot "不可能"。比較 The news may not be true.The news can't be true .(4) may(might)(not)+have done(been) 表對過去或完成時的揣測。Someth