2. 外语
  3. Throughout history man has had to accept the fact that all living things must die. But people now live longer than they【C1】_____

Throughout history man has had to accept the fact that all living things must die. But people now live longer than they【C1】_____

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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【C1】______. Yet, all living things still show the【C2】______of aging, which will eventually【C3】______death. Aging is not a disease,(but)as a person passes maturity, the cells of the body and the【C4】______they form do not function as well as they【C5】______in childhood and teenage years. The body provides less【C6】______against disease and is more【C7】______to have accident. A number of related causes may【C8】______aging. Some cells of the body have a(fairly)long life, but they are not【C9】______when they die. As a person ages,【C10】______of brain cells and muscle cells decreases.【C11】______body cells die and are(replaced)by new cells. In an aging person the【C12】______cells may not be as workable or as capable【C13】______growth as those of a young person. Another【C14】______in aging may be changes within the cells【C15】______. Some of the protein chemicals in cells are known【C16】______with age and become less elastic. This is why the skin of old people wrinkles and【C17】______. This is also the reason why old people【C18】______in height. There may be other more important chemical changes in the cells. Some complex cell chemicals, such as DNA and RNA, store and【C19】______information that the cells need. Aging may affect this【C20】______and change the information carrying molecules so that they do not transmit the information as well.
【C5】
选项 A、do
B、has done
C、did
D、had done
答案C
解析 语法知识。分析句子结构可知，空格处指代的是前文提及function，句中in childhood说明时态为一般过去式，故应用助动词did代替function，故答案为C。
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