1、情态动词的基本用法.ppt

* * * * * * * * * * Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile . Copyright 2004-2011 Aspose Pty Ltd. 1、 情态动词的基本用法 (1)can、be able to 和could ①can和be able to都表示能力，意思上没多大区别。但can只有现在和过去时，而be able to则有更多的形式。但当成功地完成某一具体动作时，通常不用could而用was/were able to来表示。这时was/were able to 相当于managed to，表示经过一番努力，终于能够完成某事。 Can you use chopsticks? The wounded man still was able to get to the village and was saved in the end. Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile . Copyright 2004-2011 Aspose Pty Ltd. ②can和could can和could都可以表示能力、技能、许可、建议或请求和可能性。但比较委婉客气地提出问题或陈述看法，一般用could，回答时则用can。 Could you help me carry the bag? Can I help you? Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile . Copyright 2004-2011 Aspose Pty Ltd. He may be sick.(生病的可能性较大) — He might be sick.(生病的可能性较小) (2)may/might ①may/might表示可能，但may比might可能性大。如：-Why isn’t he in class? Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile . Copyright 2004-2011 Aspose Pty Ltd. ②may/might表示“允许”，may用于现在时或将来时，might常用在间接引语中表过去时，但might也可用于现在时间，表示比较委婉的语气，回答用may。 He says we may leave. He said we might leave. Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile . Copyright 2004-2011 Aspose Pty Ltd. Yes, you can / may. — No, you mustn’t ③may / might 表示建议或请求，但might比may?更客气，意思更肯定而无过去时态的含义。 —May / Might I use your bike? Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile . Copyright 2004-2011 Aspose Pty Ltd. （3）must ①must表示必须，应该，没有时态变化。 You must do everything as I do. ②must表示肯定的推测。 The light is still on, so he must be at home. ③mustn’t 表示禁止做某事。 You mustn’t smoke in the office. Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile . Copyright 2004-2011 Aspose Pty Ltd. （4）have to have to 表示“必须、不得不”，是由于某种外界（客观）原因而“必须”，“不得不”做某事，也可表示经常的或习惯性的事“必须”做。have to的否定形式表示不必。have to可用于多种时态中。 You will have to clean your own boots when you join the army. I have to be at my office eve