问句　肯定回答否定回答
Need you…?Yes, I must.　No,I needn't
Must you…?　/don't have to.

典型例题
1）---Could I borrow your dictionary?
---Yes, of course, you____.　
　 A. might　B. will　 C. can　 D. should
　 答案C.could表示委婉的语气，并不为时态。答语中of course，表示肯定的语气，允许某人做某事时，用can和 may来表达，不能用could或might。复习： will 与you连用，用来提出要求或下命令。should与you 连用，用来提出劝告。

2）---Shall I tell John about it?
---No, you ___. I've told him already.
　 A. needn'tB. wouldn'tC. mustn'tD. shouldn't
　 答案A。needn't 不必，不用。 wouldn't 将不, 不会的。 mustn't 禁止、不能。 shouldn't　不应该。本题为不需要，不必的意思，应用needn't。

3）---Don't forget to come to my birthday party tomorrow.
---______.
A. I don't　 B.　I won't　 C. I can't　D. I haven't
答案B.　will既可当作情态动词，表请求、建议、也可作为实义动词表"意愿、意志、决心"，本题表示决心，选B。