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Question

Difficulty: MediumNecessary Assumption

Historian: Excavations at the eighth-century settlement of Dunhaven revealed subterranean storage pits containing charred barley alongside rye grains infested with a species of grain weevil that reproduces exclusively in stored grain. Because no physical traces of aboveground storage structures were found at Dunhaven, some archaeologists have concluded that the settlement stored all of its harvested grain exclusively in these underground pits. However, this specific weevil species cannot survive winters in the subterranean humidity characteristic of Dunhaven's clay soil. Therefore, Dunhaven's residents must have utilized aboveground grain storage facilities that have left no trace in the archaeological record.

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

  1. A
    Barley is substantially less vulnerable to humidity-induced spoilage in underground pits than rye.
  2. The infested rye grains found at Dunhaven had been stored at the settlement through at least one winter season.Answer
  3. C
    Any eighth-century settlement that utilized aboveground grain storage built timber granaries that decomposed completely.
  4. D
    If a grain pest cannot survive underground conditions, grain stored in those conditions will remain free of all insect contamination.
  5. E
    Maintaining aboveground granaries was the only viable method for eighth-century farmers to prevent weevil infestations.

Answer

The infested rye grains found at Dunhaven had been stored at the settlement through at least one winter season.
The argument concludes that aboveground storage must have existed solely based on the fact that weevils cannot survive winter in subterranean clay pits. This inference holds only if the weevils were present during a winter at Dunhaven. If the infested rye was consumed, processed, or discarded before winter arrived, the weevils never had to survive an underground winter, removing any necessity for aboveground storage structures.

Step-by-Step Solution

1
Identify the conclusion and premises of the stimulus
Conclusion: Dunhaven's residents must have used unrecorded aboveground grain storage facilities. Premises: Grain weevils reproduce only in stored grain; they cannot survive winter in the humid underground pits at Dunhaven.
Establishing the logical gap between the premises and the conclusion isolates what must be assumed.
2
Evaluate the missing link required for the premise about winter survival to support the conclusion
The argument infers that aboveground storage was necessary because weevils cannot survive winter underground. For this limitation to force an aboveground facility, the weevils must have actually had to survive a winter at Dunhaven.
If the grain was not kept through a winter, winter survival constraints cannot necessitate alternative winter storage.
3
Apply the Negation Test to verify necessity
Negation: The infested rye grains found at Dunhaven were NOT stored at the settlement through any winter season. If true, the weevils never needed to survive a winter at Dunhaven, eliminating the need for aboveground winter storage and collapsing the conclusion.
A necessary assumption must fatally undermine the argument when negated.

Key Concept

Necessary Assumption (Defender Model)
Estimated Time:1m 20s
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Topics

Necessary Assumption

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