I would go with E

Found explanation is some forum....
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A. nothing is stated about lending support

B. nothing is stated about increasing govt revenue

C. proceeding sentence discusses a loophole for the rich in the progressive system... not the poor. Closing the loophole would not penalize the poor.

D. Hold

E. The author's definition of fairness is not discussed (trap).

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Answer: D

Explanation: Not A because high income groups find the present system beneficial they will not support new proposal.

Not B because we don’t know rate of tax so we cannot know if collections will be more than present system

C is not possible for same reason.

E says ‘any progressive tax system’ whereas the passage indicates the progressive system is ideally supposed to achieve just that.

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Which of the following best completes the passage below?
One tax-reform proposal that has gained increasing support in recent years is the flat tax, which would impose a uniform tax rate on incomes at every level. Opponents of the flat tax say that a progressive tax system, which levies a higher rate of taxes on higher-income taxpayers, is fairer, placing the greater burden on those better able to bear it. However, the present crazy quilt of tax deductions, exemptions, credits, and loopholes benefits primarily the high-income taxpayer, who is consequently able to reduce his or her effective tax rate, often to a level below that paid by the lower-income taxpayer. Therefore, ______
(A) higher-income taxpayers are likely to lend their support to the flat-tax proposal now being considered by Congress

inverted conclusion


(B) a flat-tax system that allowed no deductions or exemptions would substantially increase actual government revenues

Who cares about govt revenues...OUT OF SCOPE
(C) the lower-income taxpayer might well be penalized by the institution of a flat-tax system in this country

Wrong!

(D) the progressive nature of our present tax system is more illusory than real

Correct... present tax system is illusory than it seems.

(E) the flat tax would actually be fairer to the lower-income taxpayer than any progressive tax system could be

Wrong

I went by elimination and got the correct answer.

(A) Totally opposite of what is given.

(E) the flat tax would actually be fairer to the lower-income taxpayer than any progressive tax system could be
We can't predict future.

(B) a flat-tax system that allowed no deductions or exemptions would substantially increase actual government revenues

Depends on other factors also.

(C) the lower-income taxpayer might well be penalized by the institution of a flat-tax system in this country

Possible but not conclusive.

(D) the progressive nature of our present tax system is more illusory than real
Given paragraph shows how the present tax is factually opposite of what it looks like. Correct option.

In my opinion D is the most logical one.