Houses built during the last ten years have been found to contain indoor air pollution at levels that are, on...
GMAT Critical Reasoning : (CR) Questions
Houses built during the last ten years have been found to contain indoor air pollution at levels that are, on average, much higher than the levels found in older houses. The reason air-pollution levels are higher in the newer houses is that many such houses are built near the sites of old waste dumps or where automobile emissions are heavy.
Which of the following, if true, calls into question the explanation above?
Passage Analysis:
| Text from Passage | Analysis |
| Houses built during the last ten years have been found to contain indoor air pollution at levels that are, on average, much higher than the levels found in older houses. |
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| The reason air-pollution levels are higher in the newer houses is that many such houses are built near the sites of old waste dumps or where automobile emissions are heavy. |
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Argument Flow:
The argument starts with an observation about pollution differences between old and new houses, then immediately offers a location-based explanation for why this difference exists.
Main Conclusion:
New houses have higher indoor air pollution because they are built near old waste dumps or areas with heavy automobile emissions.
Logical Structure:
This is a causal argument where the author takes an observed effect (higher pollution in new houses) and claims a specific cause (poor location choices near pollution sources). The logic assumes that location is the primary factor explaining the pollution difference.
Prethinking:
Question type:
Weaken - We need to find information that reduces our belief in the author's explanation for why newer houses have higher indoor air pollution
Precision of Claims
The author makes a specific causal claim: newer houses have higher pollution BECAUSE they're built near waste dumps or heavy traffic areas. We need to respect the fact that newer houses do have higher pollution levels.
Strategy
Look for alternative explanations or evidence that shows the author's reasoning is flawed. We can't dispute that newer houses have more pollution, but we can challenge whether location near dumps/traffic is the real reason. Think about what else could cause this difference or what evidence would make us doubt this location-based explanation.
This choice tells us that new houses have air-filtration systems that remove indoor pollutants. However, this doesn't weaken the author's explanation about location being the cause of higher pollution. If anything, this makes the pollution problem in new houses seem even more puzzling - despite having filtration systems, they still have higher pollution than older houses. This could actually support the idea that external sources (like dumps and traffic) are overwhelming these filtration systems.
This choice explains that relaxed smokestack emission standards have increased air pollution in homes generally. However, this doesn't help us understand why specifically newer houses have higher pollution than older houses. Both old and new houses would be affected by increased smokestack emissions, so this doesn't explain the observed difference between old and new houses that the author is trying to explain.
This choice states that new houses in rural areas have relatively low pollution levels. This actually supports rather than weakens the author's explanation. If new houses in secluded rural areas (away from dumps and traffic) have low pollution, this is consistent with the author's claim that location near pollution sources is what causes the higher pollution in other new houses.
This choice discusses weather conditions affecting air movement and pollution concentration. Like Choice B, this would affect both old and new houses equally, so it doesn't help explain the specific difference between older and newer houses that the author is addressing. Weather patterns don't distinguish between house age.
This choice identifies pressboard as a new construction material that emits formaldehyde into houses. This directly challenges the author's explanation because it provides an alternative, internal source of pollution that would specifically affect newer houses (since pressboard is described as a new material). Instead of external location factors, this suggests the pollution comes from the construction materials themselves. This creates doubt about whether location near dumps and traffic is really the primary cause of higher pollution in new houses.