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Difficulty: HardIdentifying Unstated Assumptions

To reduce the severity of summer wildfires, a municipal forestry board plans to replace mechanical brush-clearing with controlled goat grazing along park perimeters. Mechanical clearing leaves behind dry, shredded plant residue that remains combustible on the forest floor for several months. In contrast, goats consume underbrush completely, eliminating ground residue. The board concludes that substituting goat grazing for mechanical clearing will significantly decrease the overall intensity of wildfires in these perimeters during the dry season.

Which of the following is an assumption on which the forestry board's argument depends?

  1. A
    Goat grazing is substantially less expensive per acre to deploy than operating mechanical brush-clearing equipment.
  2. The goats used for controlled grazing will not preferentially avoid the most flammable shrub species in favor of fire-resistant vegetation.Answer
  3. C
    Shredded plant matter left by mechanical clearing decomposes more rapidly in humid perimeters than in arid perimeters.
  4. D
    Mechanical brush-clearing machinery generates exhaust sparks that have occasionally ignited small spot fires during operation.
  5. E
    Park perimeter areas experience significantly higher visitor traffic during dry summer months than central wilderness zones.

Answer

The argument assumes that the goats will not selectively avoid consuming the specific shrub species that contribute most to fire intensity.
The conclusion asserts that replacing mechanical clearing with goat grazing will decrease wildfire intensity because goats consume underbrush without leaving flammable ground residue. For this plan to succeed, the goats must actually eat the vegetation that creates the high fire risk. If the goats preferentially avoid the most flammable plants, those hazardous fuels will remain in the forest perimeter, rendering goat grazing ineffective at reducing fire intensity. Therefore, the argument depends on the assumption that goats will not selectively bypass the most flammable plants.

Step-by-Step Solution

1
Deconstruct the argument structure
Premise 1: Mechanical clearing leaves combustible shredded residue. Premise 2: Goats consume underbrush completely without leaving ground residue. Conclusion: Goat grazing will significantly decrease overall wildfire intensity compared to mechanical clearing.
Identifying premises and conclusion exposes the logical leap between total plant consumption and effective fire mitigation.
2
Identify the logical gap
The author assumes that goat grazing effectively removes the key combustible vegetation without introducing new vulnerabilities (such as leaving highly flammable plant species untouched).
The conclusion relies on the physical reduction of wildfire fuel.
3
Apply the Negation Test to the correct option
Negated statement: Goats WILL preferentially avoid the most flammable shrub species and consume fire-resistant vegetation instead. If true, the primary fire hazards remain standing, which destroys the conclusion that fire intensity will decrease.
A valid unstated assumption must be essential; its negation shatters the author's reasoning.

Key Concept

Identifying Unstated Assumptions via the Negation Test
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Topics

Identifying Unstated Assumptions

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