As people continue to grow and age, our body systems continue to change. At a certain poin

t 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.When people become aging, they will lose some of their ability to bounce back from disease and injury, "bounce back" here meansA.to improve in health after one's disease and injuryB.to recover from disease and injuryC.to jump after recoveringD.to run fast