Throughout history, man has had to accept the fact that all living things must die, but people now live longer than they used to

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问题     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【C1】______things still show the effect of aging, which will eventually【C2】______death. The body and the【C3】______, they do not function as well as they【C4】______in childhood and adolescence(青春期). The body provides less【C5】______against disease and is more prone(易于……的)【C6】______accident.
    A number of related causes may【C7】______to aging. Some cells of the body have a【C8】______long life, but they are not【C9】______when they die. As a person ages,【C10】______of brain cells and muscle cells decreases.  Other body cells did and are replaced by new cells. In an aging person the【C11】______cells may not be as viable(能生存的)or as capable【C12】______growth as those of a young person.
    Another factor in aging may be changes within the cells【C13】______. Some of the protein chemicals in cells【C14】______known to change【C15】______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【C16】______. There may be other more important chemical changes in the cells. Some complex cell chemicals.【C17】______DNA and RNA, store and【C18】______information that the cells need. Aging may【C19】______this process and change the information carrying molecules【C20】______they do not transmit the information as well.
【C13】

选项 A、themselves
B、itself
C、by themselves
D、of themselves

答案A

解析 themselves 与 the cells同位。by on self作“独自地、独立地”解,但并不强调会给自己带来好处。of oneself 作“自动的、自己”或“自然地”解。
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