Question 6 asks the following:
Which one of the following, if true, would be the most reasonable response for the author of passage B to make to the final argument of passage A?
So, we need to find "the final argument of passage A."
Going to the later area of passage A, we see that "the final argument" appears to be the following:
Under the
systems operating in most developed countries, the
incentives for high-income earners to avoid tax (legally or
otherwise) are enormous; and the opportunities to do
(25) so, which arise from the very complexity of the
codes, are commensurately large. So it is unsurprising
that high-income earners usually pay about as much
tax under new flat-tax regimes as they would have
paid under the previous codes.
So, we need to find a response that counters that argument and fits the agenda of the author of passage B, which is to argue in favor of graduated tax regimes.
Let's now go to the answer choices.
(A) Even under a flat-tax regime, it will be possible for some with high incomes to avoid taxes by underreporting their incomes.
This could be an argument against switching to a flax tax regime in general, but it's not a respond that counters the final argument in (A) since that final argument is based on the fact that high earners wouldn't end up paying any less under flat tax regimes because they have ways of avoiding taxes under graduated regimes, and this choice doesn't counter that argument.
(B) Existing tax codes allow tax avoidance by those with high incomes mainly because they contain loopholes and special deductions, not because they are graduated.
This choice is an effective response to the final argument because it points out that it's not the fact that tax regimes are graduated that allows the tax avoidance that the final argument mentions. It's all the loopholes and deductions that do. In other words, this choice points out that the final argument in passage (A) doesn't really effectively show that gradated tax regimes can't result in those with high incomes paying more than they would a under flat tax regime. Rather it shows that certain forms of graduates tax regimes that currently exist and involve loopholes and deductions don't result in those with high incomes paying more than they would under flat tax regime.
(C) It is unfair to those with high incomes to single them out as tax avoiders, since people at all income levels have been known to try to avoid taxes, sometimes illegally.
This choice misses the point of the final argument in passage A. The point of the final argument is not to judge or single out the tax avoidance of those with high incomes.
(D) Most taxpayers prefer a system that affords them opportunities for avoiding taxes over one that does not afford such opportunities.
This choice misses the point of the author of passage (B). The author of passage (B) is not arguing in favor of systems that afford taxpayers opportunities for avoiding taxes. In fact, the author of passage (B) would likely prefer a system that does not afford high income taxpayers opportunities for avoiding taxes.
(E) The goal of reducing tax avoidance would be advanced by eliminating income taxes altogether in favor of taxes on consumption of goods and services.
This choice is completely off topic. The author of passage (B) is arguing in favor of using a graduated tax system not about ways of reducing tax avoidance.
So, the correct answer is (B).