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As people continue to grow and age, our body systems continue to change. At a certain point in your life your body systems will begin to weaken. Your joints may become stiff. It may become more difficult for you to see and hear. The slow change of aging causes our bodies to lose some of their ability to bounce back from disease and injury. In order to live longer, we have always tried to slow or stop this process that leads us toward the end of our lives.
Many factors contribute to your health. A well-balanced diet plays an important role. The amount and type of exercise you get is another factor. Your living environment and the amount of stress you are under is yet another. But scientists studying senescence (衰老) want to know: Why do people grow old They hope that by examining the aging process on a cellular level medical science may be able to extend the length of life.

Why are some scientists interested in studying senescence ？（）
A. They want to increase the general ability of our bodies.
B. They may be able to find a better way to our life.
C. If they can pin down the biochemical process that makes us age, there will be hope for extending the length of life.
D. They want to find out if there is a link between how efficiently a cell could repair itself and how long a creature lives.