Phoenix, in the southwestern United States, has grown from an agricultural community to a city of more than 1.5 million...

GMAT Critical Reasoning : (CR) Questions

Source: Mock

Critical Reasoning

Misc.

MEDIUM

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Notes

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Phoenix, in the southwestern United States, has grown from an agricultural community to a city of more than 1.5 million residents. One consequence is that the average temperatures in the area have risen significantly: buildings and city streets are absorbing greater amounts of the sun's radiant energy and retaining more heat. This phenomenon is known as the Urban Heat Island (UHI) effect. These increased temperatures have led to increased water use for residential lawns and gardens. To conserve the city's limited water supplies by reducing the average area of garden and lawn around homes, city planners should require that residential lot sizes in new construction be smaller.

The recommendation above is most vulnerable to criticism on the grounds that it

takes for granted that reducing the size of residential lots would reduce the UHI effect and thus reduce water consumption

takes for granted that the UHI effect is the main environmental challenge faced by the city of Phoenix

fails to consider that there are ways of obtaining additional reductions in water consumption

fails to envisage the possibility that many Phoenix residents may be opposed to the plan

fails to consider the possible impact on water consumption if having a smaller proportion of grassy area were to increase the UHI effect

Solution

Passage Analysis:

Text from Passage	Analysis
Phoenix, in the southwestern United States, has grown from an agricultural community to a city of more than 1.5 million residents.	What it says: Phoenix transformed from farming area to major city with 1.5+ million people What it does: Sets up the context of rapid urban growth What it is: Background information Visualization: Agricultural area → 1.5 million person city
One consequence is that the average temperatures in the area have risen significantly: buildings and city streets are absorbing greater amounts of the sun's radiant energy and retaining more heat.	What it says: City growth caused temperatures to rise because buildings/streets absorb and hold more heat What it does: Links the urban growth to a specific environmental problem What it is: Causal explanation Visualization: More buildings + streets = More heat absorption = Higher temperatures
This phenomenon is known as the Urban Heat Island (UHI) effect.	What it says: The temperature increase has a scientific name - Urban Heat Island effect What it does: Provides technical label for the temperature problem just described What it is: Definition/labeling
These increased temperatures have led to increased water use for residential lawns and gardens.	What it says: Higher temps make people use more water for their yards and gardens What it does: Connects the temperature problem to a water consumption issue What it is: Additional consequence Visualization: Higher temps → More watering needed → Increased water use
To conserve the city's limited water supplies by reducing the average area of garden and lawn around homes, city planners should require that residential lot sizes in new construction be smaller.	What it says: City should mandate smaller lots for new homes to save water by reducing yard space What it does: Presents the author's recommended solution to the water problem What it is: Author's conclusion/recommendation Visualization: Smaller lots = Less lawn/garden space = Less water needed

Argument Flow:

The argument flows from cause to effect to solution: Phoenix grew rapidly → this caused higher temperatures (UHI effect) → higher temperatures increased water use for yards → therefore, we should require smaller lots to reduce yard space and save water.

Main Conclusion:

City planners should require smaller residential lot sizes in new construction to conserve water.

Logical Structure:

The premises establish a causal chain (urban growth → heat → water use), then the conclusion jumps to a solution (smaller lots) that targets one link in this chain. The logic assumes that reducing lot size will effectively address the water conservation problem without considering other factors.

Prethinking:

Question type:

Misc - This is asking us to identify a flaw or weakness in the reasoning that makes the recommendation vulnerable to criticism

Precision of Claims

The argument makes specific claims about causation (UHI effect causes increased water use) and proposes a specific solution (smaller lot sizes). We need to find gaps in this logical chain.

Strategy

Look for flaws in the reasoning that connects the problem to the proposed solution. Focus on assumptions the author makes that might not hold true, alternative explanations not considered, or ways the solution might not actually solve the problem or could create new issues.

Answer Choices Explained

takes for granted that reducing the size of residential lots would reduce the UHI effect and thus reduce water consumption

This mischaracterizes the argument's logic. The argument doesn't claim that smaller lots will reduce the UHI effect itself - rather, it suggests smaller lots will reduce water consumption by reducing the lawn area that needs watering due to the UHI effect. The argument accepts the UHI effect as a given and tries to work around it, not eliminate it.

takes for granted that the UHI effect is the main environmental challenge faced by the city of Phoenix

The argument doesn't need to establish that UHI is the main environmental challenge. It only needs to show that water conservation is important enough to justify the recommendation. The argument focuses specifically on water usage, and whether other environmental issues exist is irrelevant to this particular solution.

fails to consider that there are ways of obtaining additional reductions in water consumption

This isn't a flaw because the argument isn't claiming this is the only way to reduce water consumption. The question asks what makes the recommendation vulnerable to criticism, and the fact that other solutions might exist doesn't undermine this particular recommendation. We can pursue multiple approaches simultaneously.

fails to envisage the possibility that many Phoenix residents may be opposed to the plan

Resident opposition is a practical implementation concern, not a logical flaw in the reasoning itself. The argument is making a case for why the policy should be implemented based on water conservation benefits. Public opinion doesn't affect whether the logical reasoning is sound.

fails to consider the possible impact on water consumption if having a smaller proportion of grassy area were to increase the UHI effect

This identifies a crucial flaw in the argument's reasoning. The recommendation assumes that smaller lots (meaning less grassy area) will reduce water consumption. However, it fails to consider that reducing vegetation might actually worsen the Urban Heat Island effect, since grass and gardens help cool areas while concrete and buildings increase heat. If smaller lots lead to higher temperatures, water usage could actually increase overall, undermining the entire recommendation.

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