A、To give us some advice before we travel abroad. B、To offer us some important facts about handshaking. C、To introduce us to som

Handshaking, though a European practice, is often seen in big cities of China. Nobody knows exactly when the practice started in Europe. It is said that long long ago in Europe when people met, they showed their unarmed hands to each other as a sign of goodwill. As time went on and trade in cities grew rapidly, people in cities began to clap each other’s hands to make a deal or to reach an agreement. This practice was later changed into shaking hands among friends on meeting or leaving each other. "Let’s shake hands on it" sometimes means agreement reached.
    Do the Europeans shake hands wherever they go and with whomever they meet? No. Sometimes the Chinese abroad reach out their hands too often to be polite. It is really very impolite to give your hand when the other party, especially when it is a woman, shows little interest in shaking hands with you and when the meeting does not mean anything to him or her. Even if, for politeness, he holds out his unwilling hand in answer to your uninvited hand, just touch it slightly. There is generally a misunderstanding among the Chinese that westerners are usually open and straightforward, while the Chinese are rather reserved in manner. But in fact some people in western countries are more reserved than some Chinese today. So it is a good idea to shake hands with a westerner only when he shows interest in further relations with you.
Questions 20 to 22 are based on the passage you have just heard.
20. What is the purpose of people putting out their unarmed hands to each other in the old days in Europe?
21. Which statement is true according to the passage?
22. What is the main purpose of the passage?