42.One state adds a 7 percent sales tax to the price of most products purchased within its jurisdicton.This tax,therefore,if viewed as tax on income,has the reverse effcet of the federal income tax;the lower the income,the higher the annual percentage rate at which the income is taxed. The conxlusion above would be properly drawn if which of the following were assumed as a premise? A.The amount of money citizens spend on products subject to the state tax tends to be equal across income levels. B.The federal income tax favors citizens with high incomes,whereas the atate sales tax favors citizens with low incomes . C.Citizens with low annual incomes can affors to pay a relatively higher percentage of their incomes in state sales tax,since their federal income tax is relatively low. D.The lower a state's sales tax,the more it will tend to redistribute income from the more affluent citizens to the rest of society E.Citizens who fail to earn federally taxable income are also exempt from the state sales tax. 正确答案是A,解释上面是说转化成数学去思维很容易得出，但我仍不是很明白，哪位能完全理解的帮我讲解一下吧 提前谢谢了 | 
