In the Caucasus region of the Soviet Union, nearly 50 out of every 100,000 people live to celebrate their 100th birthday, and many don't stop at 100. By comparison, in America only 3 people in 100,000 reach 100. But these Soviet old people aren't alone. The Pakistani Hunzas, who live high in the Himalaya Mountains, and the Vilcabambans of the Andes Mountains in Ecuador seem to share the secret of long life too.

These peoples remain healthy in body and spirit despite the passage of time. While many older persons in industrial societies become weak and ill in their 60s and 70s, some Soviet Georgians, aged 110 to 140, work in the fields beside their great-great-grandchildren. Even the idea of aging is foreign to them. When asked, "At what age does youth end?" most of these old people had no answer. Several replied, "Well, perhaps at age 80." The very youngest estimate was age 60.

What accounts for this ability to survive to such old age, and to survive so well? First of all, hard physical work is a way of life for all of these long-lived peoples. They begin their long days of physical labor as children and never seem to stop. For example, Mr. Rustam Mamedov is 142 years of age. He re members his life experiences: the Crimean War of 1854; the Turkish War of 1878; the Bolshevik Revolution in 1917. His wife is 116 years old. They have been married for 90 years. Mr. Mamedov has no intentions of retiring from his life as a farmer. "Why? What else would I do?" he asks. Oh, he's slowed down a bit. Now he might quit for the day after 6 hours in the field instead of 10. All these people get healthful rewards from the environment in which they work. They all come from mountainous regions. They live and work at elevations of 5,000 to 12,000 feet ( 1,660 to 4,000 meters) above sea level. The air has less oxygen and is pollution-free. This reduced-oxygen environment makes the heart and blood vessel system stronger.

Another factor that may contribute to the good health of these people is their isolation. To a great ex tent, they are separated from the pressures and worries of industrial society.

Inherited factors also play some role. Most of the longest-lived peoples had parents and grand-parents who also reached very old ages. Good family genes may, therefore, be one factor in living longer.

Finally, although these three groups don't eat exactly the same foods, their diets are similar. The Hunzas, Vilcabambans, and Soviets eat little animal meat. Their diets are full of fresh fruits, vegetables, nuts, grains, cheese, and milk. They never eat more food than their bodies need.

It is clear that isolation from urban pressures and pollution, clean mountain air, daily hard work, moderate diets, good genes, and a youthful approach to life all contribute to the health and remarkable long life of all these people.

What is the main subject of this passage?

A．Mr. Mamedov's life.

B．A description of several societies where people live a long time.

C．Suggestions for how you can live a long life.

D．Hard physical work is a good way to live a long time.