may表示請求和允許,意為可以.
may的否定回答可用can't,mustn't,may not表示“不可以”、“禁止”、“阻止”.can't,mustn't,may not都可以無條件替換么不可以。從虛擬語氣上來說 may最弱 must最強(qiáng)。may not 語氣較弱，”可以不”，You may not finish your homework;can't ”不能”; You can't be too serious;問句回答時：Can I go out to play? No, you can't. 或做may問句的回答：May I sit here? No, you can't.;mustn't 語氣強(qiáng)，”禁止”:You mustn't step on the grass.選項(xiàng)里這三個都有的話，是不是要分析語境就行了是的。具體情況具體分析。