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.
【C1】

选项 A、either
B、so
C、nor
D、never

答案C

解析 选项必须既能引导倒装句,又能与前面的否定相呼应。either表示“也”,可以用在否定句中,但一般放在句尾;so可以引导倒装句,但它用在肯定句中,表示“也”,nor也可以引导倒装句,并可用在否定句中,构成not...nor…(既不……也不……)固定结构,never也可以引导倒装句,表示否定,但它必须放在句首。故选C。
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