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 ttherefore strongly related to the after-tax price of a pack of cigarettes. Which of the following, if true, would most strengthen the argument above? ['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.', 'Most consumers were unaware that the tax on cigarettes was going to increase.', 'The information available to consumers on the health risks of smoking remained largely unchanged in the period before and after the tax increase.', '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.']