单选题 The price of maple syrup has jumped front 22 dollars a gallon three years ago to 40 dollars a gallon today. It can be concluded that maple-syrup harvesters have been artificially inflating prices and that governmental price regulations are necessary to control rising prices.
Which of the following, if true, casts the most doubt on the conclusion drawn above?

A、 The government already requires maple-syrup harvesters to submit their facilities to licensing by the health department.
B、 Insect infestation and drought have stunted the growth of syrup-producing maple trees and caused leas-abundant syrup harvests.
C、 Maple syrup is produced in rural areas that suffer from high unemployment.
D、 Technological improvements in maple-syrup harvesting have reduced production costs.
E、 (E) Maple-syrup prices have risen many times in the past, though never before at the rate recently observed.

【正确答案】 B

【答案解析】[解析] 本题是由一个事实“枫糖价格上涨”，而得出了一个解释性的结论：枫糖的采集者人为地抬高了价格，属于“B，A”题型，这个推理的成立所隐含的假设为：除了A以外无其他因素影响B。但这道题目是反对。如果由于虫害和干旱阻碍了枫树生长并造成枫糖短缺，那么段落推理所隐含的假设就不成立，所以推理结论必不正确，因此(B)为正确答案。(E)易误选，但(E)只表明过去枫糖价格上涨多次，但是不是采集者所为我们并不知道，所以(E)为无关选项。请大家注意：“that government price regulations are necessary to control rising prices”是上面推理的一个Suggestion。