The purpose of keeping fit is to avoid illness, avoid the mental and physical fatigue（疲劳）, and above all to feel more pleasure in being alive. Research has shown the value of a balanced diet, fresh air, sunshine, enough rest and some forms of regular exercise for everyone. If everyone followed this plan, the number of people visiting the doctor and going to hospital would be reduced.
Unfortunately, although most people acknowledge the importance of physical fitness, not enough of us put this into practice. We spend too much time watching others from the comfort of an armchair or a seat in the stand at a sports stadium.
One reason why people who are physically fit to live longer is that they do not put the heart under excessive strain（过度劳累）and so they reduce the risk of heart and blood vessel（血管）diseases. They also avoid suffering weakened muscles, which are the cause of a great deal of trouble.
All in all, sensible exercise, suited to each person and properly undertaken on the advice of a doctor, is the best insurance of meeting these requirements.
Why do people want to keep fit?

A．Because they want to avoid health.

B．Because they want to add mental and physical fatigue.

C．Because they want to feel happier and live longer.

D．Because they want to obtain much more money.

Which of the following is TRUE according to the passage?

A．Everyone knows the importance of this plan.

B．Not all people do what the plan tells them to do.

C．Most people put the plan into practice.

D．No one wants to do with this plan.

What does the passage mainly talk about?

A．Balanced diet is the most important.

B．People who are physically fit live longer.

C．Most people can live longer.

D．People always do not put the heart under excessive strain.