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Question

Difficulty: MediumPassage Assumptions and Underlying Premises

Read the following passage carefully:

To address worsening groundwater depletion in rapidly growing Tier-2 cities, several municipal corporations have recently mandated the installation of rooftop rainwater harvesting systems for all commercial buildings exceeding a specified square footage. Municipal authorities argue that this regulatory measure will recharge local aquifers and reduce municipal dependence on expensive long-distance water pipeline transfers during summer months. Additionally, city planners highlight that capturing stormwater at the roof level will prevent urban flash flooding during peak monsoon downpours, thereby preventing severe storm-drain overflows. Consequently, municipal boards are preparing to issue compliance notices to commercial property owners, projecting a significant improvement in urban water security within two years.

Which one of the following is the most crucial underlying assumption made by the author in the passage above?

  1. Commercial rooftops constitute a sufficient proportion of the urban catchment area in these cities to yield a measurable impact on groundwater recharge and flood control.Answer
  2. B
    Constructing long-distance water transfer pipelines is inherently less sustainable than local groundwater extraction.
  3. C
    Commercial building owners will universally support the municipal mandate without raising legal or administrative objections.
  4. D
    Installing rooftop rainwater harvesting systems completely eliminates the necessity for municipal storm-drain maintenance during monsoons.

Answer

The statement asserting that commercial rooftops constitute a sufficient proportion of the urban catchment area to yield a measurable impact on groundwater recharge and flood control.
The author concludes that mandating rainwater harvesting specifically on commercial buildings will significantly recharge groundwater and mitigate urban flooding. For this conclusion to hold, it must be assumed that commercial rooftops account for a large enough portion of the urban surface area to produce those physical results. If their surface area were negligible, the policy would not lead to the projected outcome.

Step-by-Step Solution

1
Identify the author's main conclusion
The main conclusion is that mandating rooftop rainwater harvesting on large commercial buildings will significantly improve urban water security and reduce monsoon flash flooding within two years.
An assumption is an unstated premise required to bridge the gap between the given evidence (the mandate) and the conclusion (improved water security).
2
Apply the Negation Test to candidate assumptions
Negating the option regarding catchment area yields: 'Commercial rooftops do NOT constitute a sufficient proportion of the urban catchment area to yield a measurable impact on groundwater recharge and flood control.'
If the negated statement is true, the mandate on commercial rooftops would fail to achieve significant water security or flood reduction, causing the author's main argument to collapse.
3
Evaluate remaining options against distractor patterns
Other options rely on external facts, extreme language ('universally support'), or misinterpretations of infrastructure requirements ('completely eliminates maintenance').
Valid passage assumptions must be strictly necessary for the author's specific line of reasoning, not external generalizations or extreme claims.

Key Concept

Identifying Unstated Premises via the Negation Test
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Topics

Passage Assumptions and Underlying Premises

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