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还是没有改好
Maize contains the vitamin niacin, but not in a form the body can absorb. Pellagra is a disease that results from niacin deficiency. When maize was introduced into southern Europe from the Americas in the eighteenth century, it quickly became a dietary staple, and many Europeans who came to subsist primarily on maize developed pellagra. Pellagra was virtually unknown at that time in the Americas, however, even among people who subsisted primarily on maize. Which of the following, if true, most helps to explainthe contrasting incidence of pellagra described above?
A Once introduced into southern Europe, maize became popular with landowners because of its high yields relative to other cereal crops.
B Maize grown in the Americas contained more niacin than maize grown in Europe did.
C Traditional ways of preparing maize in the Americas convert maize’s niacin into a nutritionally useful form.
D In southern Europe many of the people who consumed maize also ate niacin-rich foods.
E Before the discovery of pellagra’s link with niacin, it was widely believed that the disease was an infection that could be transmitted from person to person.
个人选择C，解释一下原因：
题干中给出的facts是：
1. Maize 中包含维他命niacin, 但是人体不能吸收这个维他命niacin
2. niacin不足，导致pellagra这种病
3. maize从美洲引入欧洲以后，成为一种主食，而主要食用这个maize的欧洲人得了pellagra
4. 但是在美州，以maize作为主食的人，却没有得过pellagra的病
题目问的问题是，为啥欧洲人美洲人都已maize为主食，但是美洲人不得病？
根据facts 1&2 可以知道，如果直接吃maize, 由于niacin不能被吸收，因此会得pellagra. 这个可以解释欧洲人得pellagra。另一方面，美洲人不得pellagra, 说明他们不缺少niacin。niacin可以有几个来源，比如他们吃的麦子里的niacin, 由于经过处理，变得可以吸收（对应C选项），或者他们吃的其他食物里有可以被吸收的niacin（选项中没有，但是如果有，可以作为正确答案）
总结起来其实就是：
欧美人民都吃麦子，但是：
欧洲人的食物中的niacin不能被吸收
美洲人的食物中的niacin能被吸收（同上面的解释，这个niacin的来源其实有两个）
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发表于 2015-11-28 21:08:23
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