阅读理解 Throughout history man has had to accept the fact that all living things must die, but people now live longer than they used to. Yet, all (47)________ things still show the effect of aging, which will eventually result in death, the body and the (48)________ they form do not function as well as they did in childhood and adolescence (青春期)- The body provides less (49)________ against disease and is more prone (易于……的) to accident. A number of related causes may (50)________ to aging. Some cells of the body have a (51)________ long life, but they are not (52)________ when they die. As a person ages, number of brain cells and muscle cells decreases. Other body cells did and are replaced by new cells. In an aging person the (53)________ cells may not be as viable(能生存的) or as capable of growth as those of a young person. Another factor in aging may be changes within the cells (54)________. Some of the protein chemicals in cells are known to change with age and become less elastic. This is why the skin of old people wrinkles and hangs loose. This is also the reason old people shrink in (55)________ There may be other more important chemical changes in the cells. Some complex cell chemicals. Such as DNA and RNA, store and pass on information that the cells need. Aging may (56)________ this process and change the information carrying molecules so that they do not transmit the information as well. WORD BANK A. brains B. contribute C. replaced D. high E. living F. protection G. fairly H. new I. itself J. affect K. lively L. organs M. rearranged N. themselves O. height