A. organs B. being changed C. fact D. process E. for F. reborn G. to H. shorten I. to change J. recovered K. of L. old M. lengthen N. reason O. remaining Throughout history man has had to accept the fact that all living things must die, but people now live longer than they used to. However, all living things still show the 1)__________ of aging, which will eventually result in death. Aging is not a disease, but as a person passes maturity, the cells of the body and the 2)____________they form do not function as well as they did in childhood and adolescence. The body provides less protection against disease and is more inclined 3)___________accident. A number of related causes may contribute to aging. Some cells of the body have a fairly long life, but they are not 4)__________ when they die. As a person ages, the number of brain cells and muscle cells decreases. The other body cells die and are replaced by new cells. In an aging person the 5)__________cells may not be as viable or as capable 6)___________growth as those of a young person. Another 7)____________ in aging may be changes within the cells themselves. Some of the protein chemicals in the cells are known 8)_____________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 9)_______________in height. There are maybe other more important chemical changes in the cells. Some complex cell chemicals, such as DNA, store and pass on information that the cells need. Aging may affect this 10)_____________ and change the information-carrying molecules so that they do not transmit the information as well.