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Difficulty: MediumStrengthen

Marine Archaeologist: Bronze artifacts recovered from seventeenth-century shipwrecks often suffer rapid corrosion known as 'bronze disease' when exposed to atmospheric oxygen and humidity. In a recent preservation trial, conservators submerged several newly excavated bronze cannons in a sodium sesquicarbonate solution for six months. Following the treatment, none of the submerged cannons developed active bronze disease during two years of atmospheric exposure. The conservators concluded that the sodium sesquicarbonate wash effectively leaches destructive cuprous chlorides out of ancient bronze, thereby preventing post-excavation corrosion.

Which of the following, if true, most strengthens the conservators' argument?

  1. A
    Bronze artifacts treated with sodium sesquicarbonate undergo structural embrittlement that makes them more vulnerable to physical fracturing when handled.
  2. B
    Wrought iron artifacts recovered from the same underwater site required electrochemical reduction rather than chemical immersion baths to stabilize their surfaces.
  3. C
    All maritime metal relics excavated from saltwater environments will inevitably disintegrate within weeks unless immediately submerged in chemical stabilizers.
  4. Untreated bronze cannons recovered from the same shipwreck and stored in the exact same atmospheric conditions developed active bronze disease within four months of excavation.Answer
  5. E
    The electrochemical reactions responsible for bronze disease progress at a significantly higher rate in warm coastal air than in cold mountain air.

Answer

Untreated bronze cannons recovered from the same shipwreck and stored in the exact same atmospheric conditions developed active bronze disease within four months of excavation.
The correct response provides an essential experimental control by demonstrating that identical bronze cannons from the same wreck corroded quickly when left untreated under identical storage conditions. This confirms that the test environment was conducive to bronze disease and strongly supports the conclusion that the chemical wash was the causal mechanism preventing deterioration.

Step-by-Step Solution

1
Analyze the argument structure
Premises establish that newly excavated bronze cannons submerged in sodium sesquicarbonate showed no bronze disease for two years. The conclusion asserts that the chemical wash caused this preservation by leaching destructive chlorides.
Identifying the premises and conclusion isolates the causal gap between the observed outcome and the attributed cause.
2
Identify the logical vulnerability
The argument lacks a control group; without knowing what would have happened without the wash, the absence of disease could be due to low atmospheric humidity, inherent artifact resistance, or chance.
Strengthening a causal conclusion often requires establishing a controlled comparison or eliminating alternative explanations.
3
Evaluate the strengthening impact of the correct choice
Showing that untreated cannons from the same site under identical atmospheric conditions rapidly corroded confirms that the corrosion trigger was present and that the wash was responsible for preventing the reaction.
A valid control group directly reinforces the causal link between the intervention and the successful preservation outcome.

Key Concept

Strengthening Causal Claims via Control Comparison
Estimated Time:1m 30s
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