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Zorluk: OrtaNecessary Assumption

Arboriculturist: Urban street trees planted in compacted soil frequently suffer from stunted root growth due to poor soil aeration. A municipal agency recently began inoculating the soil around newly planted street saplings with a specialized mycorrhizal fungus, observing that saplings receiving this treatment developed root systems thirty percent deeper and wider than untreated saplings over a two-year period. The agency concluded that the fungal inoculation successfully enhanced soil aeration around the saplings' roots.

Which one of the following is an assumption on which the municipal agency's argument depends?

  1. A
    Any street sapling treated with the specialized mycorrhizal fungus will establish a healthy root system regardless of initial soil compaction levels.
  2. B
    Soil aeration around newly planted street saplings cannot be significantly improved without the introduction of mycorrhizal fungi.
  3. The greater root development observed in the inoculated saplings was not caused entirely by factors that promote growth independently of soil aeration.Cevap
  4. D
    Inoculating compacted soil with mycorrhizal fungi is sufficient to completely eliminate all negative effects of soil compaction on urban trees.
  5. E
    The specialized mycorrhizal fungus is more effective at promoting root expansion than standard mechanical soil-decompaction techniques.

Cevap

The statement that the greater root development was not caused entirely by factors that promote growth independently of soil aeration.
The argument reasons from an observed effect (enhanced root expansion) to a specific cause (enhanced soil aeration), based on the background fact that poor aeration stunts roots. For this inference to hold, it must be true that the expanded root growth was at least partly dependent on an improvement in aeration. If the growth was entirely driven by an alternative mechanism that operates independently of aeration, the expanded roots would offer no evidence of improved aeration.

Adım Adım Çözüm

1
Analyze the argument structure
Premise 1: Compacted soil stunts roots due to poor aeration. Premise 2: Inoculated saplings grew roots 30% deeper and wider than untreated saplings. Conclusion: The inoculation enhanced soil aeration.
Identifying the premises and the main conclusion exposes the logical gap between root growth and aeration improvement.
2
Identify the unstated assumption linking root growth to soil aeration
The author infers that aeration improved solely because root growth increased, implicitly ruling out the possibility that the fungus stimulated root growth through mechanisms unrelated to aeration.
If the fungus stimulated growth without affecting aeration, the conclusion is invalid.
3
Apply the Negation Test
Negating the statement gives: 'The greater root development was caused entirely by factors that promote growth independently of soil aeration.' This directly severs the link between increased root size and enhanced aeration, causing the agency's conclusion to fail.
A necessary assumption must fatally undermine the conclusion when logically negated.

Anahtar Kavram

Necessary Assumption & The Negation Test
Tahmini Süre:1m 25s
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Necessary Assumption

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