Gortland has long been narrowly self-sufficient in both grain and meat.
However, as per capita income in Gortland has risen toward the world
average, per capita consumption of meat has also risen toward the world
average, and it takes several pounds of grain to produce one pound of meat.
Therefore, since per capita income continues to rise, whereas domestic
grain production will not increase, Gortland will soon have to import
either grain or meat or both.
Which of the following is an assumption on which the argument depends?
(A) The total acreage devoted to grain production in Gortland will soon
decrease.
(B) Importing either grain or meat will not result in a significantly
higher percentage of Gortlanders' incomes being spent on food than is
currently the case.
(C) The per capita consumption of meat in Gortland is increasing at roughly
the same rate across all income levels.
(D) The per capita income of meat producers in Gortland is rising faster
than the per capita income of grain producers.
(E) People in Gortland who increase their consumption of meat will not
radically decrease their consumption of grain.
答案是E，请nn帮忙解释一下，同时理一下这道题的思路，感谢！ | 
