单项选择题

Directions:This part is to test your reading ability.There are five tasks for you to fulfill.Youshould read the reading materials carefully and do the tasks as you are instructed．
TASK 1
Directions:After reading the following passage,you will find five questions or unfinshedstatements numbered from 36 to 40.For each question or statement there are four choicesmarkted A,B,C and D.You should make the correct choice and mark the corresponding letter onthe Answer Sheet with a single line through the center．

As people continue to grow and age,our body systems continue to change.At a certain pointin your life your body systems will begin to weaken.Your strength may become weaker.It may become more difficult for you to see and hear.The slow change of aging causes our bodies tolose come of their ability to bounce back from disease and injury.In order to live longer,we have always tried to slow or stop this change that leads us toward the end of our lives. Many factors decide your health.A good diet plays an important role.The amount and typeof exercise you get is another factor.Your living condition is yet another.But scientists studying aging problem want to know:Why do people grow oldThey hope that by studying the aging medical science they may be able to make the length of life longer. There is nothing to be afraid of as old age comes.Many consider the later part of life to bethe best time for living.Physical activity may become less.but often you get better understanding of yourself and the world． What we consider old age now may only be middle age some day soon.Who knows,with somany advances in medical science happening so quickly,life span may one day be measured incenturies,rather than in years．

Many consider the later part of life to be the best time of living,because______．