prep-2-50 不懂正确答案的意思

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?（相当于问assumption）
逃税导致税收制定者制定更高的税额，从而导致更多的逃税

(A) An increase in tax rates tends to function as an incentive for taxpayers to try to increase their pretax incomes. 税率提高导致纳税人努力提高税前收入。回答yes，削弱，因为可以收到的税，就不用继续增加税率了，回答no，加强
(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. 回答yes，加强，因为别的方法得不偿失，所以要增加税率，回答no, 无法判断，因为不知道会不会使用这些手段
(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. 这个可以
(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. 回答yes，不一定能解决问题，以为不一定能够得到预期的税收；回答no，加强
(E) Taxpayers do not differ from each other with respect to the rate of taxation that will cause them to evade taxes. 回答yes，无关，回答no,无关again
cr2详解中题目加解答就是这样的，但是既然是assumption的题，为什么要用evaluate 的方法来解答呢？不懂c 选项是什嘛意思。。