A、To explain why people keep talking. B、To persuade people to stop making noises. C、To encourage people to join in conversations

Silence is unnatural to man. He begins life with a cry and ends it in stillness. In between he does all he can to make a noise in the world, and he fears silence more than anything else. Even his conversation is an attempt to prevent a fearful silence. If he is introduced to another person, and a number of pauses occur in the conversation, he regards himself as a failure. He knows that ninety-nine percent of human conversation means no more than the buzzing of a fly, but he is anxious to join in the buzz and to prove that he is a man and not a waxwork figure.
    The aim of conversation is. for the most part, to communicate ideas; it is to keep up the buzzing sound. There are, it must be admitted, different qualities of buzz; there is even a buzz that is as annoying as the continuous noise made by a mosquito. But at a dinner party one would rather be a mosquito than a quiet person. Most buzzing, fortunately, is pleasant to the ear, and some of it is pleasant even to the mind. He would be a foolish man if he waited until he had a wise thought to take part in the buzzing with his neighbours.
    Those who hate to pick up the weather as a conversational opening seem to me not to know the reason why human beings wish to talk. Very few human beings join in a conversation in the hope of learning anything new. Some of them are content if they are merely allowed to go on making a noise into other people’s ears. They have nothing to tell them except that they have seen two or three new plays or that they had food in a Swiss hotel. At the end of an evening, during which they have said nothing meaningful for a long time, they just prove themselves to be successful conversationalists.
Questions 20 to 22 are based on the passage you have just heard.
20. What is people’s purpose in making conversation according to the speaker?
21. What do people usually talk about to their neighbours according to the passage?
22. What is the speaker’s purpose in giving this speech?