A、The art of saying thank you. B、The secret of staying pretty. C、The importance of good manners. D、The difference between elegan

Do you remember a time when people were a little nicer and gentler with each other? I certainly do. And I feel that much of the world has somehow gotten away from that. Too often I see people rushing into elevators without giving those inside a chance to get off first, or never saying "thank you" when others hold a door open for them. We get lazy and in our laziness we think that something like a simple "thank you" doesn’t really matter. But it can matter very much.
    The fact is that no matter how nicely we dress or how beautifully we decorate our homes, we can’t be truly elegant without good manners, because elegance and good manners always go hand in hand. In fact, I think of good manners as a sort of hidden beauty secret. Haven’t you noticed that the kindest, most generous people seem to keep getting prettier? It’s funny how that happens, but it does. Take the long-lost art of saying "thank you" like wearing a little make-up, or making sure your hair is neat. Getting into the habit of saying "thank you" can make you feel better about yourself. Good manners add to your image, while an angry face makes the best dressed person look ugly.
19. What is the passage mainly about?
20. What does the speaker say about people of the past?
21. How can we best improve our image, according to the passage?