2. 外语
  3. Throughout history man has had to accept the fact that all living things must die, hut people now live longer than they used to.

Throughout history man has had to accept the fact that all living things must die, hut 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, hut 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【C19】______. 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.
【C14】
选项 A、is
B、are
C、was
D、were
答案B
解析 主语some of the protein chemicals为复数；而且，从后中句become中得到提示，用一般现在时，描述一种客观规律。
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大学英语四级

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