题目内容：

In the Caucasus region of Russia, 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 Russian old people aren’t alone. The Pakistanis, who live high in the Himalaya Mountains, and the Ecuadorans of the Andes Mountains seem to share the secret of long life, too.

    These people 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 Caucasians aged 100 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.”

    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 people. 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. His wife is 116 years old. They have been married for 90 years. Mr. Mamedov has no intention of retiring from his life as a farmer. “Why？What else would I do？”he asks. 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 1,660 to 1,000 meters above sea level. The air has less oxygen and is pollution-free. This reduced-oxygen environment makes the heart and blood vessel(血管) system stronger.

    Another factor that may contribute to the good health of these people is their isolation. To a great extent, they are separated from the pressures and worries of industrial society. Inherited factors also play some role. Most of the longest-lived people had parents and grandparents who also reached very old ages. Good family genes may, therefore, be one factor in living longer.

1.The example of Mr. and Mrs. Mamedov implies that some Caucasians aged 100 to 140 ____.

A．become weak and hopeless            

B．are too old to work in the fields

C．benefit from physical work            

D．are still working in the fields

2.What is the main way of life for all of these long-lived people?

A．Retiring from their lives as farmers.    

B．Having been married for 90 years.

C．Hard physical work.                  

D．Having no intentions.

3.Which of the following factors isn’t helpful to people’s health and long life?

A．Clean mountain air.        B．Daily hard work.

C． Good genes             D． Stress and pressure.