In the past the country of Malvernia has relied heavily on imported oil. Malvernia recently implemented a program to convert heating systems from oil to natural gas. Malvernia currently produces more natural gas each year than it uses, and oil production in Malvernian oil fields is increasing at a steady pace. If these trends in fuel production and usage continue, therefore, Malvernian reliance on foreign sources for fuel is likely to decline soon.

Which of the following would it be most useful to establish in evaluating the argument?

(A) When, if ever, will production of oil in Malvernia outstrip production of natural gas?

(B) Is Malvernia among the countries that rely most on imported oil?

(C) What proportion of Malvernia's total energy needs is met by hydroelectric, solar, and nuclear power?

(D) Is the amount of oil used each year in Malvernia for generating electricity and fuel for transportation
increasing?

(E) Have any existing oil-burning heating systems in Malvernia already been converted to natural-gas-burning
heating systems?
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D it must be...

Sure of the OA? Its OG question right?
Yep Q 74 Og 12 Ans is D.What if the country’s need for oil was going to rise drastically in the coming years?

Hi guys,

Looks like there's some confusion on this one, so let's give it a closer look. Thabk's emphasis on the conclusion is important (and correct). When a CR question asks what would be most useful to evaluate "the argument", really it is asking you what would help evaluate the conclusion. The conclusion here is clearly marked by the keyword "therefore": "Malvernian reliance on foreign sources for fuel is likely to decline soon."

And what would help evaluate the conclusion? An answer choice that will (depending on what is established) either strengthen or weaken that conclusion. So really, you can treat this kind of question as either Strengthen or Weaken, but in my experience it's usually easiest to treat these "useful to evaluate" questions as Weaken. Think of it this way: The author's argument is missing some information (what it would be useful to establish), and therefore there is a gap between his evidence and his conclusion. The correct answer would expose that gap, just as it would in a standard Weaken question.

To the stimulus. On first reading, it seems like a pretty reasonable argument. The Malvernians have relied on imported oil in the past, but they may be able to turn that around, for two reasons:

1. They're switching from oil to natural gas, of which they have a plentiful supply.
2. Domestic oil production is increasing.

If domestic oil supply is going up and demand is going down, it seems almost inevitable that their reliance on imported oil will decrease. However, note the limited scope of the first premise: they aren't switching ALL oil usage to natural gas, only the fuel used in their heating systems. We actually don't know anything about the overall demand for oil. That is the gap in the author's reasoning. Choice D exploits this gap: if the amount of oil used for non-heating purposes (generating electricity and transportation) is increasing, then the overall demand for oil might still be increasing too fast for domestic oil production to keep pace (even though production is increasing as well).

E seems to be the most popular wrong answer choice, so let's talk about that one too. It references the heating systems mentioned in the stimulus, so it's tempting. However, remember that we need to evaluate the conclusion. Will the fact that some oil-burning systems have already been converted to natural gas affect whether Malvernian reliance on foreign sources for fuel "is likely to decline soon"? Not really. Whether the conversions have already started or not, they will happen, so in effect this answer neither adds to nor takes anything away from the argument. Now, you could get into all sorts of complicated logic to convince yourself that E is the answer -- Like, maybe because the conversions have started, that means that the all the conversions will happen faster, and maybe if the conversions happen faster it's more likely that reliance on foreign oil will decline soon... Maybe, maybe, maybe. This kind of speculative thinking is never required on the GMAT (and in fact can be disastrous). The correct answer on a Strengthen or Weaken question must DIRECTLY affect the conclusion -- not after multiple steps. Don't overthink CR answer choices!

However, as this question shows, it is extremely important to read the stimulus carefully and note the specific wording involved. Better to spend a little extra time up front to understand the stimulus rather than flounder around with the answer choices, not knowing what you're looking for. Ideally on this question you would be able to predict, in vague from, what the answer will look like before reading the answer choices. However, this isn't always possible. As long as you have a good understanding of the stimulus you should be fine.

Hope that sheds some light on this question.

Happy studying...
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Mark

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+1 for D - The devil in disguise
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Gonna make it this time

Thank you experts,
you said that we should predict what to look for in the answer choices . I do not understand this point, pls explain more. we predict what and how we predict. when do you do this predicting? for what kind of question we do this predicting. How do the predicting help? do veritas write any book on this point, pls explain,share.