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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 explain the contrasting incidence of pellagra described above?
- Once introduced into southern Europe, maize became popular with landowners because of its high yields relative to other cereal crops.
- Maize grown in the Americas contained more niacin than maize grown in Europe did.
- Traditional ways of preparing maize in the Americas convert maize’s niacin into a nutritionally useful form.
- In southern Europe many of the people who consumed maize also ate niacin-rich foods.
- 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.
题目：解释矛盾现象：欧洲人吃了玉米还会得病，但美洲人吃了不会。 注意题目里在比较两个地区的人
同因却不同果
的现象产生的原因。 所以答案里必然要“比较（两地的）差异”。 题目里说玉米含有niacin，但身体不能直接吸收。P是niacin不足引起的。这里有个“Gap”，就是吸收与否才是是否得病的关键点！
A，玉米由于高产量受欢迎，无关；
B，玉米在美洲比在欧洲含有的niacin含量高。 这个选项涉及了比较两地，容易误选这个。 但如玉米果还是以不能直接吸收的方式存在，那美洲人一样不能吸收里面的niacin营养物质，还是会得P病，因此B也不对；
C，美洲人的食用方式让玉米里的nicain转化为更有营养的吸收方式； 架桥，弥补了“Gap”——尽管也吃的是不能直接吸收的玉米，但美洲人的食用方式让玉米里的niacine变得可以吸收了，因此不会得P病。
D，有的欧洲人吃玉米的同时还吃nicain含量高的食物，无关； 吃得再多，如果比吸收一样没用，还是会得P病，不能解释美洲人不得病的原因。
E，以前认为P这个病还会传染，无关。
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发表于 2008-10-12 22:32:00
