How to Find the Right Answer in Critical Reasoning

In Critical Reasoning, it is often possible to foresee the correct answer without even glancing at the answer choices. Whenever a question asks you to strengthen or weaken an argument, the correct answer will usually be the one that fixes the inconsistency between the conclusion and the premise of the passage. Inference questions can be extremely open ended, but strengthen/weaken (can I abbreviate this to streaken?) questions are generally about the most glaring issue with a sentence. The GMAT uses this type of trick a lot, so the errors may be subtle and they may be crafty, but they are always present in any strengthen/weaken CR question.

Plans and predictions make up a special subdivision of strengthen or weaken questions, as the plan hasn’t necessarily been executed yet or the prediction hasn’t yet come to pass (think Sarah Connor in the first two Terminator movies). There is still time to change the future, but only if we act now and change the variables of the equation. Plans on the GMAT have not yet been executed, so theoretically we can modify them a little to match our needs.

Consider the following question:

Offshore oil-drilling operations entail an unavoidable risk of an oil spill, but importing oil tankers presently entails an even greater such risk per barrel of oil. Therefore, if we are to reduce the risk of an oil spill without curtailing our use of oil, we must invest more in offshore operations and import less oil on tankers.

Which of the following, if true, most seriously weakens the argument above?

(A)   Tankers can easily be redesigned so that their use entails less risk of an oil spill.

(B)   Oil spills caused by tankers have generally been more serious than those caused by offshore operations.

(C)   The impact of offshore operations on the environment can be controlled by careful management.

(D)   Offshore operations usually damage the ocean floor, but tankers rarely cause such damage.

(E)    Importing oil on tankers is currently less expensive than drilling for it offshore.

This question is asking us to weaken the argument above. The argument’s conclusion is that we must invest more in offshore operations and import less oil on tankers. Why? The premise of the argument is that oil tankers currently provide a bigger risk of spilling oil per barrel of oil. The question even has the diamond in the rough word “presently”, which hints that this situation could change. Without even looking at the answer choices, we can surmise that this situation isn’t set in stone and can therefore be changed.

In other words: how do we weaken the argument above? Well, what if it simply weren’t true anymore? The whole argument hinges on tankers being more risky. So if new information or new technology allowed the tankers to become safer than their offshore counterparts, the entire argument would fall apart. Let’s sift through the answers to see if any of these match our needs:

(A)   Tankers can easily be redesigned so that their use entails less risk of an oil spill.

Well this is pretty much exactly what we’re shooting for. Let’s see if any of the other choices make us reconsider this choice. (a choice that’s equivalent to Arnold’s classic: “come with me if you want to live”)

(B)   Oil spills caused by tankers have generally been more serious than those caused by offshore operations.

This option is actually a 180°, as it strengthens the argument. We shouldn’t use tankers because tankers are more dangerous. Perfect strengthener. These options can be very tempting, as they are excellent answers, except for the lack of the word “not”, which is somewhat crucial in this case.

(C)   The impact of offshore operations on the environment can be controlled by careful management.

Much like answer choice B, this actually strengthens the argument. At this point you might start wondering if you’re misinterpreting the question, as the majority of the choices seem to contradict your interpretation. This is a classic GMAT ploy, so don’t fall for it. This underscores again why making a prediction is crucial in these situations.

(D)   Offshore operations usually damage the ocean floor, but tankers rarely cause such damage.

This argument is discussing oil spills, so whether the environmental damage is limited to the seafloor or the seashells (and whether she sells seashells by the sea shore) is irrelevant to the issue.

(E)    Importing oil on tankers is currently less expensive than drilling for it offshore.

The economic argument is frequently a compelling one, especially for aspiring business students, but the focus is on the environment impact of oil spills, not whether I can get premium gas for a few cents cheaper. This is out of scope of the issue.

The correct answer is (A).

The difference between getting the correct answer and getting swept up in the possible traps on each question hinges on correctly predicting what will weaken (or strengthen) a question. The prediction need not always be perfect, but it should get you thinking of the answers in a different light. If you spend even 10 or 15 seconds reflecting on what the correct answer must look like, you reduce the chances of falling for a clever trap or a tricky 180° choice that lures you into the murky depths of the GMAT open water.

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Ron Awad is a GMAT instructor for Veritas Prep based in Montreal, bringing you weekly advice for success on your exam.  After graduating from McGill and receiving his MBA from Concordia, Ron started teaching GMAT prep and his Veritas Prep students have given him rave reviews ever since.

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