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  3. Vitamins are organic compounds necessary in small amounts in the diet for the normal growth and maintenance of life of animals,

Vitamins are organic compounds necessary in small amounts in the diet for the normal growth and maintenance of life of animals,

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问题     Vitamins are organic compounds necessary in small amounts in the diet for the normal growth and maintenance of life of animals, including man.
    They do not provide energy, 【C1】______do they construct or build any part of the body. They are needed for【C2】______foods into energy and body maintenance. There are thirteen or more of them, and if 【C3】______is missing a deficiency disease becomes【C4】______.
    Vitamins are similar because they are made of the same elements—usually carbon, hydrogen, oxygen, and【C5】______nitrogen. They are different【C6】______their elements are arranged differently, and each vitamin【C7】______one or more specific functions in the body.
    【C8】______enough vitamins is essential to life, although the body has no nutritional use for 【C9】______vitamins. Many people, 【C10】______, believe in being on the "safe side" and thus take extra vitamins. However, a well balanced diet will usually meet all the body’s vitamin needs.
【C3】
选项 A、any
B、some
C、anything
D、something
答案A
解析 空格所在句子是一个由and连接的并列句，前一个分句There are thirteen or moreof them中的them指的是vitamins，后一个分句是一个由if引导的条件状语从句，意为“如果……缺乏，(会出现)维生素缺乏症。”由于if引导的从句中谓语动词is是单数，因而，只能由一个表示单数意义的不定代词作为被选项。首先排除some，它一般用于肯定句，做主语时谓语动词用复数；其次anything与something泛指任何事或某些事，放入句中不符句意；any放入后相当于any of them，即“任何维生素”。注意any一般用于否定或疑问句中．做主语时，谓语动词常用单数，故选A。
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