听力原文：W: You know, I've often wondered why people laugh at the picture of a big belly businessman slipping on a banana skin and falling on his bottom. We are to feel sorry for him. M: Actually, Laura, I think we laugh because we are glad it didn't happen to us. But of course there is also a kind of humorous satisfaction in seeing somebody self-important making a fool of themselves. W: Yes, and then there are a lot of jokes about people who are too fat or physically handicapped, you know, deaf, or short-sighted, things like that. After all, it's not really funny to be like that. M: Oh, I think that's because we're embarrassed. We don't know how to cope with the situation. Perhaps we are even a bit frightened we might get like that, so we laugh. What about the custard pie routine? W: What do you mean 'custard pie routine'? M: You know, all those old films where someone gets so outraged with his boss, he picks up a custard pie and plasters it all over the other person's face. W: That never makes me laugh very much, because you can guess it's going to happen. But a lot of people still find it laughable. It must be because it's the sort of the thing we'd all love to do once in a while and never quite have the courage to. M: I had an old aunt who used to throw cups of tea at people when she was particularly irritated. She said it relieved her feelings. W: It must have come a bit expensive. M: Not really. She took care never to throw her best china. Questions: 19. Why does the man say we laugh when we see some self-important people making fools of themselves? 20. Why do some people joke about those who are fat or handicapped according to the man? 21. Why do many people find it funny to see someone throwing a custard pie on their boss's face? 22. Why did the man's aunt say she would drop cups of tea at people occasionally? (23)