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Difficulty: MediumFlaw in the Reasoning

Transit Director: For any metropolitan area to achieve a net reduction in downtown carbon emissions, it is necessary to convert its entire municipal bus fleet to zero-emission electric vehicles. Last month, Metro City successfully completed the full conversion of its municipal bus fleet to electric vehicles. Therefore, Metro City will definitely achieve a net reduction in downtown carbon emissions.

The transit director's argument is most vulnerable to criticism on the grounds that it

  1. A
    fails to consider whether the operating and maintenance costs of electric buses exceed those of conventional diesel vehicles
  2. treats a condition that is necessary for achieving a reduction in emissions as if it were sufficient to guarantee that reductionAnswer
  3. C
    disputes the factual reliability of the report stating that Metro City completed its fleet conversion
  4. D
    presumes without warrant that electric bus batteries will never suffer mechanical failure or lose charging efficiency
  5. E
    confuses an intermediate conclusion regarding fleet procurement with the main conclusion regarding regional climate policy

Answer

The argument is flawed because it treats a condition that is necessary for achieving a reduction in emissions as if it were sufficient to guarantee that reduction.
The transit director establishes that converting the bus fleet is a necessary condition for achieving downtown carbon reduction ('it is necessary to convert...'). However, in the conclusion, the director infers that because this condition has been satisfied, the reduction will definitely occur. This improperly treats a requirement as a guarantee (a necessary condition as a sufficient one).

Step-by-Step Solution

1
Identify the premises and the conclusion in the stimulus
Premise 1: Reducing downtown carbon emissions requires (necessary condition) converting the municipal bus fleet to electric vehicles. Premise 2: Metro City has converted its municipal bus fleet to electric vehicles. Conclusion: Metro City will achieve a net reduction in downtown carbon emissions.
Deconstructing the argument into its structural components is essential to evaluate the validity of the inference.
2
Analyze the formal logical relationship between the premises and conclusion
The author establishes that Fleet Conversion is a necessary requirement for Emissions Reduction (Emissions Reduction -> Fleet Conversion). The author then notes that the requirement was met (Fleet Conversion occurred) and concludes that the outcome is guaranteed (Emissions Reduction).
This represents a classic conditional fallacy (affirming the consequent / confusing necessary and sufficient conditions).
3
Select the choice that accurately describes this conditional error
The correct description states that the argument mistakes a necessary condition for a sufficient one.
Meeting a necessary requirement does not ensure the final result, as other factors (such as private vehicle traffic or industrial output) could offset the reduction.

Key Concept

Conditional Reasoning Flaw (Confusing Necessary and Sufficient Conditions)
Estimated Time:1m 15s
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Topics

Flaw in the Reasoning

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