一道看不懂的OG題，求分析

梦游中的宝贝

看的糊里糊塗，找不到頭緒，看了OG的官方解釋，有句話看不懂，求大神解答。
a sharp reduction in the amoun of grain consumed could compensate for increased meat consumption。

題：
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.

francoisyang

原文的fact如下：
1. G的谷和肉正好自足；
2. G的人均收入提高；
3. G的人均吃肉量提高；
4. 几磅谷产1磅肉。
conclusion是如果谷的产量不提高，G就必须进口谷或肉。
假设人多吃肉了就会少吃谷，那在谷的产量恒定情况下，少吃的谷可以拿去产肉，那G的肉还是可以自足。
E排除了多吃肉就会少吃谷的可能。