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Difficulty: Very hardStrengthening Arguments

To protect centuries-old parchment manuscripts from humidity-induced decay, the curators of a national archive recently replaced the facility's traditional refrigeration-based cooling coils with advanced chemical desiccant air-drying units. Over the six months following the replacement, sensor logs confirmed that relative humidity in the vault remained perfectly stabilized within the ideal target range of 45% to 50%. Nevertheless, physical inspections conducted at the end of the period revealed that the rate of structural fiber cracking on the parchment manuscripts was twice as high as it had been during the six months prior to the equipment change. Concluding that the new desiccant units were directly responsible for the accelerated deterioration, the lead conservator recommended re-installing the original refrigeration-based system.

Which of the following, if true, most strengthens the lead conservator's argument?

  1. During the six months following the equipment change, manuscripts stored in an adjacent vault served by the original refrigeration-based system experienced no increase in fiber cracking, despite being handled with the same frequency as those in the updated vault.Answer
  2. B
    The chemical desiccant units consume 35 percent less electrical power per month than the older refrigeration-based cooling coils consumed during peak summer operation.
  3. C
    Inspections of modern paper documents stored under the new desiccant system showed no evidence of accelerated fiber breakdown over the same six-month period.
  4. D
    When the vault temperature was lowered by two degrees during a routine system calibration, the rate of manuscript fiber cracking under the desiccant system temporarily decreased.
  5. E
    The archived parchment manuscripts were produced using historical animal skin preparation techniques that make them inherently more fragile than 19th-century rag paper.

Answer

The argument is most strengthened by the evidence that manuscripts stored under the original refrigeration system in an adjacent vault suffered no increase in damage under identical handling conditions.
The correct response introduces a control group: identical manuscripts in an adjacent room kept under the old refrigeration system experienced no increase in cracking while being handled at the same rate. By keeping external conditions and handling constant between the two groups, this finding effectively rules out alternative explanations (such as seasonal shifts or handling damage) and provides strong empirical evidence that the new desiccant system caused the accelerated deterioration.

Step-by-Step Solution

1
Identify the author's premise and conclusion
Premise: Fiber cracking doubled after replacing refrigeration coils with chemical desiccant units, even though relative humidity remained constant. Conclusion: The chemical desiccant units caused the damage, so the original refrigeration system should be restored.
Understanding the precise causal link claimed by the author is essential to identifying strengthening evidence.
2
Evaluate potential logical gaps or alternative explanations
The increase in cracking could have been caused by unmeasured external variables (e.g., seasonal weather shifts, increased archival handling, ambient temperature fluctuation) rather than the desiccant units themselves.
Strengthening a causal argument requires ruling out plausible alternative causes or providing a control group.
3
Select the option that confirms causality by controlling for confounding variables
Showing that manuscripts in a control vault equipped with the old system suffered no increase in damage under identical conditions rules out general environmental or handling causes and isolates the desiccant system as the driver of the damage.
A controlled comparative setup eliminates alternative explanations, directly validating the lead conservator's causal claim.

Key Concept

Causal Argument Strengthening via Control Group / Elimination of Alternative Causes
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Topics

Strengthening Arguments

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