Unit 11 Conflict and Compromise 情态动词 讲义 -2023-2024学年高中英语北师大版（2019）选择性必修第四册

情态动词 第一节 情态动词的基本用法 1 .can/could 1)能够(过去式:could.否定形式can’t/couldn’t:不能够） Nobody can stop the development of science. I can’t speak English, but I can speak some Spanish. 2)可能(不牵涉是否真的发生，客观存在的可能性） Even expert drivers can make mistakes. Mr. Reed is in poor health. He can be ill at any time. 用can表示“可能”，较多地用于否定句和疑问句，而could则不受此限 If you don’t have a guide, you could lose your way. The moon cannot always be at the full. What can he possibly mean? 3)允许(can/could无时间上的差异，只是could较为婉转，更有礼貌） You cannot leave here till I come back. Anyone can enroll for this course. 4) can’t... too… /can’t… enough 再…也不为过 You can’t be too careful/ careful enough when driving. We can’t put too much emphasis on cooperation. 2. may/might 1)或许，可能(指事实上的可能性，且might/may无时间上的差异，只是might在口气 上更加不确定，从而比较婉转） I may be busy from tomorrow on. You may catch sight of the sunrise from here when you get up before 5 in the morning. He might be still waiting at your office. 在疑问句中表示“可能”，用can/could,而不用may/ might Where can he be? Can they be angry? may/ might not有“不可能”及“不允许”两种意思，故表示“不可能”时，常用 “can’t/ couldn’t” This can’t be my handbag. She can’t love Paul. 2) 表示允许，许可（might/may无时间上的差异，只是might较为婉转，更有礼貌） May I come in? May I smoke here? 3) may可以用来表示祝愿 May you succeed. May you enjoy your holiday. 4) may/might (just) as well do不妨……，最好…… You may as well stay at home. Since it’s a fine day, we might as well walk. 3. must 1) 法律/规定上要求的或道德上是必需的，出于职责、义务该做某事 Everyone must be loyal to his motherland. All drivers must obey the traffic rules. 2) 表示出于主观意识而必须要做某事 We must keep steps to the scientific development. You must hurry up, or you’ll be late. 3) must be表示猜测、推测，常用于肯定句中表示猜测 (否定:can’t be) You must be tired after working so long. The lights are on. They must be at home. 4) 表示禁止 (用于否定句） You must not speak ill of others. You mustn’t do anything illegal. 注意：mustn’t只表示“禁止”; 若需表示“不可能”，用can’t/couldn’t; 表示“不需要”，用 needn’t 或 don’t/doesn’t/didn’t have to 4. have to/has to/had to 1) 不得不 Animals kept in this way can easily get sick, so they have