may I , could I,等这些的肯定和否定回答答:-yes, you may/can 或者sure, go ahead 等等,看情况定.一般来说,用you can 不多.-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...