情态动词和虚拟语气（讲义）通用版英语六年级下册

　情态动词和虚拟语气 　情态动词 1. 表示能力 can/could 意为“能，会” ①Many people can use the computer. ②No one could answer this challenging question. be able to do表示经过一定努力而获得的能力 2. 表示请求、允许 委婉程度might> may> could> can Can I have a word with you？It won't take long. —Might I ask for a picture of your little daughter? —Yes，you may. 3. 表示推测可能性 可能性大小must > can > could > may > might ↓ ↓ ↓ 肯定句 否定句和疑问句 肯定句和否定句 mustn't表示禁止，意为“不得，不允许；一定不要”。 That car is my property；you mustn't use it without my permission. can表示客观或理论上的可能性可以用于肯定句 ①It can be very hot here in summer. ②Accidents can happen to any drunken driver. 对现在、将来情况进行推测 情态动词+动词原形（do） 对过去情况进行推测 情态动词+have+done He can't be our manager.He has gone to Beijing. He can't have left.His coat is here。 —I don't really like James.Why did you invite him? —Don't worry.He might not come.He said he wasn't certain what his plans were. Someone must have used my umbrella yesterday.I found it wet. He is so happy.He must have won the match. She can't have read about the explosion.She didn't know anything about it. Sorry，I'm late.I might have turned off the alarm clock and gone back to sleep again. 表示祝愿，常用结构为“May＋主语＋动词原形！” May you be happy every day! must表示“必须”，语气强烈。 have to表示“不得不”，意义与must相近，但又有所区别。must表示说话人的主观看法，have to则强调客观需要；must只有一种形式，而have to有人称、时态等方面的变化。 ①—Shall I inform him of the change of the schedule right now? —I am afraid you must，in case he comes late for the meeting. ②I have to go now，because my mother is in hospital. should/ought to的用法 1．should表示责任、义务、劝告、建议等，意为“应该”。 We should be strict with ourselves. 2．should表示出乎意料的口气，意为“竟然，居然”。 Such a gentleman should do that. 这样一位绅士竟然会做那种事。 3．ought to表示义务或责任，意为“应该”，语气比should稍重。 You ought not to be late for such an important meeting. 这么重要的会议你不应该迟到的。 4．should和ought to表示推测，指预期的可能性，意为“应该，估计”。 She promised to come by 10 o'clock.She should/ought to be here at any moment. 她答应10点之前来的。她随时都可能来到。 should have done 表示本该做什么而实际上没有做 Look！There are so ma