1.can/could能力 He can sing songs in French. He could swim at the age of 3。 表示请求Can you help me carry the box into the room? Could you help me, please？ 可能性,表示有时会Jeff is clever, but sometimes he is very dull。 针对不同时间表示推测(只能用于否定句和问句）can’t doHe can’t be at home right now, for I saw him go out just now。 can't be doingHe can't be studying in the classroom， for I saw him go to the football field with a football。 can’t have doneHe can’t have finished homework so soon, for he didn't come to school yesterday。 Where can I have put my keys？ 2.may/might允许May I smoke here？ 表示祝福May you a happy life！针对不同时间表示推测（只能用于否定句和问句）may do He may come, but he is not sure。 may be doingJim may be reading in the library. may have doneHe may have left the bag in the library. 3.must肯定形式表示必须,应该；否定形式表示绝对禁止，语气强烈You must have a passport if you want to go abroad。 You mustn’t take photos here！回答 must/need 的一般疑问句时,肯 定 回 答 用 must; 否 定 回 答 用needn’t/don’t have toMust I come back home early？ Yes， you must。 Need I come back late？ No， you needn't/don’t have to。 针对不同时间表示推测（只能用于肯定句）must doTom must study hard ， for he always gets the first place every time. must be doingIt’s so noisy upstairs。 They must be quarreling again. must have doneIt must have been around 9：00, because it was totally dark。 4.shall一三人称的问句表示请求Shall he wait here？ What shall we do next? 二三人称的陈述句表示允诺,警告，命令,威胁…You shall get an answer tomorrow。 5.should劝告,建议You should see your parents regularly. 根据客观事实作出的的推断，可能性较大It's 7：20. He should come。 why/how+should 表示说话人对某Why should you be...
