[Helr题库] 请问用helr怎么解释这道题

69. Escalating worldwide demand for corn is expected to cause the market price of corn to rise sharply and remain high.  Although corn is extensively used as feed for livestock, livestock feed accounts for only a small fraction of the retail price of meat.  Therefore, the increase in corn prices is very unlikely to produce any comparable long-term increase in the retail price of meat.

Which of the following, if true, most seriously weakens the argument?

(A) The cost of shipping and handling meat has also risen sharply.

(B) Livestock producers who currently use corn to feed their livestock have the option of switching to other kinds of feed.

(C) The rising cost of feed is leading some livestock producers to leave the business, thereby reducing the future supply of meat.

(D) Worldwide demand for grains other than corn has also increased.

(E) The price of corn affects the retail price of a variety of other food products more than it affects the price of meat.

这道题按照helr的逻辑属于因果推断，

（因）前提：玉米价格上涨且玉米是喂养畜牧动物的粮食，但是喂养费仅仅占据肉类零售价很小的一部分

  （果）结论：玉米价格的上涨不太可能带来肉价的上涨

我不太懂为什么A不对，A提出了另一种可能性，正好可以反驳结论啊