One state adds a 7 percent sales tax to the price of most products purchased within its jurisdiction．This tax，therefore， if viewed as tax on income，has the reverse effect of the federal income tax：the lower the income，the higher the annual percentage rate at which the income is taxed．

The conclusion 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 state sales tax favors citizens with low incomes.

C. Citizens with low annual incomes can afford 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 states sales tax.

这道题我是一点头绪都没有，没能理解题干中包含的信息的意思和它们之间的相互关系。看选项更是茫然。希望前辈们能够帮我具体地分析和讲解一下题干和选项，感激不尽。

选a。增加7%的销售税，不管是谁买产品都得多交7%的钱（也就是a收入不同的人花在同这些商品上的钱是一样的）。把销售税看成收入所得税，税率等于税款/收入，税款相同，收入越低，税率越高。

ps.外国的个人所得税根据收入水平，对收入高的人和收入低的人实行不同的税率，防止贫富差异过大。

谢谢版主！！！