Examkin

Soru

Zorluk: OrtaStrengthen

Agricultural Scientist: In a field trial across thirty commercial apple orchards, trees treated with a foliar spray containing live *Bacillus* bacteria produced fruit with significantly lower rates of bitter rot fungal infection than untreated trees did. Because chemical analyses revealed that the spray did not alter the thickness or acidity of the apple skin, the scientist concluded that the *Bacillus* bacteria themselves actively suppress the germination of bitter rot fungal spores on the fruit's surface.

Which of the following, if true, most strengthens the agricultural scientist's argument?

  1. A
    In laboratory assays, bitter rot fungal spores germinate at identical rates regardless of whether live *Bacillus* bacteria are present in the culture medium.
  2. B
    Commercial apple growers who do not use biological bacterial sprays typically rely on synthetic chemical fungicides to manage fungal outbreaks.
  3. Trees sprayed with a sterile solution identical to the foliar spray in every respect except lacking live *Bacillus* bacteria experienced rates of bitter rot infection comparable to those of untreated trees.Cevap
  4. D
    The specific strain of *Bacillus* bacteria utilized in the trial is the single most effective biological control agent ever documented against agricultural pathogens.
  5. E
    Commercial apple orchards situated in humid regional climates generally exhibit higher baseline frequencies of bitter rot infection than those in arid climates.

Cevap

The statement showing that trees sprayed with a sterile solution containing all spray ingredients except the live bacteria suffered infection rates comparable to untreated trees.
The argument concludes that live *Bacillus* bacteria were the direct cause of the lower infection rates. A major vulnerability of this inference is that the liquid spray itself or other inactive carrier ingredients might have washed away spores or created a hostile environment. By showing that an identical spray without live bacteria yields infection rates no better than no treatment at all, the correct choice acts as a negative control, ruling out the carrier solution as an alternative cause and strongly reinforcing the causal role of the bacteria.

Adım Adım Çözüm

1
Identify the premises and conclusion of the argument.
Premise: Apple trees sprayed with a bacterial mixture had lower bitter rot infection rates than untreated trees, without changes to apple skin thickness or acidity. Conclusion: The live bacteria themselves actively suppress fungal spore germination.
Clarifying the boundary between observed evidence and the causal claim reveals the reasoning gap.
2
Isolate the unstated assumption and potential alternative explanations.
The author assumes that no other element of the foliar spray application (such as the liquid carrier, surfactant, or physical moisture) caused the reduction in fungal infection.
Causal conclusions in experimental settings require establishing that the proposed independent variable, rather than confounding treatment factors, generated the outcome.
3
Evaluate the answer choices for information that eliminates confounding variables or substantiates the causal link.
Demonstrating that an identical spray lacking only the bacteria produces no therapeutic effect confirms that the bacteria are necessary for the observed protection.
Ruling out a potential alternative cause directly strengthens a causal argument.

Anahtar Kavram

Causal strengthening via ruling out confounding variables and establishing negative controls
Tahmini Süre:1m 15s
Bu soruyu puanla

Konular

Strengthen

Bu konudan daha fazla soru