求解几道CR题

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Q16:
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?

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.

Q20:
Scientists typically do their most creative work before the age of forty.  It is commonly thought that this happens because aging by itself brings about a loss of creative capacity.  However, studies show that a disproportionately large number of the scientists who produce highly creative work beyond the age of forty entered their field at an older age than is usual.  Since by the age of forty the large majority of scientists have been working in their field for at least fifteen years, the studies’ finding strongly suggests that the real reason why scientists over forty rarely produce highly creative work is not that they have simply aged but rather that they generally have spent too long in a given field.

In the argument given, the two portions in boldface play which of the following roles?

A. The first is the position that the argument as a whole opposes; the second is an objection that has been raised against a position defended in the argument.
B. The first is a claim that has been advanced in support of a position that the argument opposes; the second is a finding that has been used in support of that position. ×
C. The first is an explanation that the argument challenges; the second is a finding that has been used in support of that explanation.
D. The first is an explanation that the argument challenges; the second is a finding on which that challenge is based.
E. The first is an explanation that the argument defends; the second is a finding that has been used to challenge that explanation.

In Teruvia, the quantity of rice produced per year is currently just large enough to satisfy domestic demand.  Teruvia’s total rice acreage will not be expanded in the foreseeable future, nor will rice yields per acre increase appreciably.  Teruvia’s population, however, will be increasing significantly for years to come.  Clearly, therefore, Teruvia will soon have to begin importing rice.

Which of the following is an assumption on which the argument depends?

A. No pronounced trend of decreasing per capita demand for rice is imminent in Teruvia.
B. Not all of the acreage in Teruvia currently planted with rice is well suited to the cultivation of rice.
C. None of the strains of rice grown in Teruvia are exceptionally high-yielding.
D. There are no populated regions in Teruvia in which the population will not increase.
E. There are no major crops other than rice for which domestic production and domestic demand are currently in balance in Teruvia. ×