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In the year following an eight-cent increase in the federal tax on a pack of cigarettes, sales of cigarettes fell ten percent. In contrast, in the year prior to the tax increase, sales had fallen one percent. The volume of cigarette sales is therefore strongly related to the after-tax price of a pack of cigarettes.
Which of the following, if true, would most strengthen the argument above?
A. During the second year after the tax increase, cigarette sales increased by a significant amount.
B. The information available to consumers on the health risks of smoking remained largely unchanged in the period before and after the tax increase.
C. Most consumers were unaware that the tax on cigarettes was going to increase.
D. During the year following the cigarette tax increase, many consumers had less income, in inflation-adjusted dollars, than they had had in the previous year.
E. During the year after the tax increase, there was a greater variety of cigarettes on the market than there had been during the previous year.
请问d选项为什么不行呢
我是这样想: 因为烟的税增加 所以烟的价钱变贵 所得就相对减少 购买力下降所以比较不会去买烟 买烟的数量下降 | 
