天山-5-14

Q14:
Maize contains the vitamin niacin, but not in a form the body can absorb.  ellagra 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?

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. （c）
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.

这道题的思路在哪？请nn指教