听力原文： Why do so many people live to a healthy old age in certain parts of the world? [31] What is the secret of their long lives? Three things seem to be very important: [29] fresh air, fresh food and a simple way of life. People work near their homes in the clean, mountain air instead of traveling long distances to work by car, bus or train. They do not sit all day in busy offices or factories, but work hard outdoors in the fields. They take more exercise and eat less food than people in the cities of the West. For years the Hunzas of the Himalayas did not need policemen, lawyers or doctors. There was no crime, no divorce and not much illness in their society. [30] They were a happy, peaceful people, famous all over India for their long, healthy lives. (30)