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There’s nothing more frustrating than preparing thoroughly for the GMAT Critical Reasoning section — poring over hundreds of complex arguments, wrapping your head around triple negations, learning to spot an assumption from a mile away — only to end up losing points for something as simple as not paying attention to the question stem.

Yet the shadowy figures behind the GMAT are bent on making sure you do just that, peppering assumption, strengthen, and weaken questions with answer choices that would be correct… if you were dealing with an inference question. Let’s take a look at an example:

In recent decades, the vast majority of construction companies have halted the use of asbestos for installation. During this same time period, word began to spread through various news media that long-term exposure to asbestos was causally linked to mesothelioma and other serious lung diseases. Therefore, the home building companies must have halted the use of asbestos in response to the new publicity given to its possible negative health consequences.

Which of the following, if true, most seriously calls into question the explanation above?

A: On average, fewer people are having homes built using asbestos insulation than in decades past.
B: People living in homes built with asbestos insulation may continue to experience health problems after the asbestos has been removed.
C: The use of asbestos insulation in industrial buildings has remained fairly constant, while its use in residences has sharply declined.
D: Sales of alternative insulation materials such as fiberglass have increased in recent decades.
E: Many alternative insulation materials that were previously prohibitively expensive have dropped considerably in price in recent decades.

If you dive right into answer choices after reading through the argument, Choice A might be really tempting. Since “the vast majority of construction companies” have stopped using asbestos, it is logically inferable from the argument that “on average” fewer people are using it in building their homes. In fact, Choice A would probably be the correct answer if this were an inference question — but it’s not!

In the Knewton course, A is a tricky answer choice that we mark with the label, “True according to the passage, but doesn’t answer the question.” The GMAT designers include it to tempt test-takers who might recognize the statement as logically true, but not notice that it doesn’t serve the purpose of weakening the argument. They even made it choice A to catch your eye, while burying the right answer further below!

The best way to avoid a “True but not correct” trap answer is to read the question stem first. This will let you know exactly what to look for as you read, whether it’s an assumption, a strengthener, a weakener, or an inference. Besides helping you avoid this particular wrong answer trap, it will also help you identify and ignore extraneous information as soon as you see it, leaving your mind less cluttered.

Now let’s go back and re-read the question stem above. The phrase “calls into question” tells you that your job is to weaken the argument.

When attempting to weaken an argument, it helps to identify the assumption it relies on and think of a way to deny it. A quick read through this argument should show you that it is a causalargument; it presents evidence that two facts are correlated (asbestos is recognized as dangerous, the use of asbestos declines) and then draws the conclusion that one fact must havecaused the other (x causes y).

Whenever an argument says that x causes y, it makes the assumption that y does not cause x and that some unknown z does not cause y. In this case, it is assumed that awareness of the negative health consequences of asbestos (x) caused a decline in its usage (y). It doesn’t make much sense for y to cause x in this case, so you should look for an answer choice that says that some other factor (z) caused y. Choice E is correct.

So remember: Read the question stem first and know what you’re looking for.  This way, trap answers won’t pop out at you as much just because they’re true according to the passage.