题目内容：

完形填空

Throughout history man has had to accept the fact that all living things must die. But people now live longer than they_________. Yet, all living things still show the__________of aging, which will eventually___________death.

Aging is not a disease, but as a person passes maturity (成熟期), the cells of the body and the__________they form do not function as well as they____________in childhood and teenage years. The body provides less__________against disease and is more_________to have an accident.

A number of related causes may___________to aging. Some cells of the body have a fairly long life, but they are not____________when they die. As a person ages, ________  of brain cells and muscle cells decreases. ________ body cells die and are replaced by new cells. In an aging person the________ cells may not be as workable or as capable   ________  growth as those of a young person.

Another ________ in aging may be changes within the cells________ . Some of the protein(蛋白质) chemicals in cells are known ________ with age and become less elastic (有弹性). This is why the skin of old people wrinkles（起皱纹）and ________ . This is also the reason why old people ________ in height. There may be other more important chemical changes in the cells. Some complex cell chemicals, such as DNA and RNA, store and  ________ information that the cells need. Aging may affect this ________  and change the information carrying molecules(分子) so that they do not transmit the information as well.

1.A. would              B. be used to          C. used to          D. used

2.A. function           B. effect              C. affect           D. sign

3.A. lead in           B. give in              C. run into        D. result in

4.A. hands             B. feet                 C. heart           D. organs

5.A. do                 B. has done             C. did             D. had done

6.A. energy             B. protection           C. prevention      D. power

7.A. likely           B. probable             C. possible         D. alike

8.A. attend         B. lead                C. add              D. devote

9.A. replaced         B. rebuilt              C. recovered      D. rearranged

10.A. a number          B. the amount           C. the number      D. a great deal

11.A. The others      B. Others               C. Another          D. Other

12.A. old              B. left                C. new              D. other

13.A. to              B. for                  C. of             D. in

14.A. factor            B. effect               C. reason          D. element

15.A. for themselves    B. of themselves        C. themselves      D. on their own

16.A. change          B. to have changed     C. to change      D. to be changed

17.A. becomes loose     B. is become loosely     C. became loosely D. is becoming loose

18.A. increase           B. shrink              C. lengthen         D. decrease

19.A. pass away          B. pass by             C. pass off         D. pass on

20.A. improvement        B. possess             C. approach         D. process