may I , could I,等这些的肯定和否定回答答:-no, you can't/mustn't. 或者no ,please don't -could i……-yes , you can/go ahead -no, you can't /please don't, you'd better not -must i ……-yes, you must.-no, you needn't/don't have to.-need i ……-yes, you need. /yes, please (do)-no, you needn...