共用题干 AgingThroughout 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 living things still show the________(51)of aging,which will eventually________(52)death.Aging is not a disease,but as a person passes maturity,the cells of the body and the________ (53) do not function as well as they did in childhood and adolescence(青春期).The body provides less________(54)against disease and is more likely________(55)have accident.A number of related causes may________(56)aging. Some cells of the body have a fairly long life,but they are not reborn when they die.As a person ages,________(57)of brain cells and muscle cells decreases.The other cells are replaced by new cells.In an aging person the________(58) cells and muscle cells may not be as viable(能生存的)or as capable________ ( 59 ) growth as those of a young person.Another________(60)in aging may be changes within the cells themselves.Some of the protein chemicals in cells are known________(61)with age and became less elastic.This is why the skin of old people wrinkles and________(62).This is also the reason old people________(63)in height. There may not be other more important chemical changes in the cells.Some complex cell chemicals, such as DNA and RNA,store and________(64)information that the cells need.Aging may affect this________(65)and change the information-carry molecules so that they do not transmit the information as well. _________(51)
A.function B.effect C.fact D.symbol正确答案B
