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VerbalCritical Reasoning

Free GMAT Critical Reasoning Practice Question

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City council member: The transit agency says its new rapid-bus line cut downtown traffic, pointing out that the average car commute downtown is three minutes shorter than a year ago. But over the same year the city also removed hundreds of on-street parking spaces downtown and converted them to traffic lanes, a change that by itself speeds car traffic. The agency's figure therefore does not establish that the rapid-bus line eased traffic.

The answer to which of the following questions would be most useful in evaluating the argument?

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Answer & Explanation

Correct answer

D

This is an Evaluate question: the most useful question is the one whose opposite answers swing the argument's force in opposite directions. The council member grants the three-minute improvement but argues it could be the work of the parking-to-lane conversions rather than the bus line. The decisive question therefore gauges how much of that improvement the conversions alone could produce.

(D) does exactly this: if the converted streets carry enough traffic that the conversions could account for the whole three minutes, the bus line is not needed to explain the figure; if they carry too little, room remains for the bus line to have helped. Yes and no point in opposite directions, so the question is genuinely useful. The same-axis same-direction near-miss is (B): it returns to the commute-improvement figure, the very number the council member already concedes and calls inconclusive, so re-confirming it cannot weigh the rival cause. The decisive sub-clause is that (D) sizes the confounding cause while (B) only re-establishes the already-granted effect.

(A), (C), and (E) raise finances, rider comfort, and other cities; none can separate the bus line from the parking conversions, the split the council member's point turns on. Only (D) sizes that confound.