请教prep-2第50题

50.  (33327-!-item-!-188;#058&007566)

When people evade income taxes by not declaring taxable income, a vicious cycle results.  Tax evasion forces lawmakers to raise income tax rates, which causes the tax burden on nonevading taxpayers to become heavier.  This, in turn, encourages even more taxpayers to evade income taxes by hiding taxable income.

The vicious cycle described above could not result unless which of the following were true?

(A) An increase in tax rates tends to function as an incentive for taxpayers to try to increase their pretax incomes.

(B) Some methods for detecting tax evaders, and thus recovering some tax revenue lost through evasion, bring in more than they cost, but their success rate varies from year to year.

(C) When lawmakers establish income tax rates in order to generate a certain level of revenue, they do not allow adequately for revenue that will be lost through evasion.

(D) No one who routinely hides some taxable income can be induced by a lowering of tax rates to stop hiding such income unless fines for evaders are raised at the same time.

(E) Taxpayers do not differ from each other with respect to the rate of taxation that will cause them to evade taxes.

这题选C，请问C是什么意思？怎么就避免这个结果了？多谢！

up up up同样困惑中

The vicious cycle described above could not result unless which of the following were true?

THIS IS A QUESTION ASKING US TO FIND OUT THE ASSUMPTION OF THE ARGUMENT