1) May I come in? Yes, you can. No, you can't.
2) May I have a cup of coffee? Yes, of course. No, we've run out of coffee.
3) May I take this book, please? Yes, you can. No, you can't.
4) May I smoke here? Yes, you can. No, you can't.
5) May I speak to you now? Yes, please. Sorry, have to go.
6) May I go out? Yes, you can. No, you can't.
7) May I have a glass of milk? Yes, of course. No, we've run out of milk.