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Difficulty: HardDistinguishing Supported and Unsupported Inferences

Closed-circuit underwater breathing apparatuses recycle exhaled gas rather than venting bubbles into the surrounding water. As a diver exhales, carbon dioxide is directed through a chemical canister filled with absorbent material, typically soda lime, which neutralizes the gas through an exothermic reaction. Electronic sensors continuously monitor the remaining partial pressure of oxygen in the breathing loop, injecting minute bursts of pure oxygen only when levels fall below a designated threshold. Consequently, the operational duration of a closed-circuit system is constrained primarily by the chemical exhaustion of the carbon dioxide absorbent rather than the volume of the gas cylinder.

Which of the following conclusions is most directly supported by the passage?

  1. A
    Military divers deploy closed-circuit breathing gear primarily to avoid acoustic detection by surface vessels.
  2. A diver's operational time limit is primarily determined by the capacity of the chemical scrubber rather than the size of the gas supply.Answer
  3. C
    The chemical neutralization of carbon dioxide occurs only after electronic sensors inject pure oxygen into the loop.
  4. D
    Closed-circuit breathing apparatuses eliminate the danger of breathing gas becoming depleted during extended dives.

Answer

A diver's operational time limit is primarily determined by the capacity of the chemical scrubber rather than the size of the gas supply.
The conclusion stating that operational time is determined by scrubber capacity rather than gas supply directly paraphrases the final sentence of the passage, which explicitly identifies the chemical exhaustion of the carbon dioxide absorbent as the primary operational constraint.

Step-by-Step Solution

1
Analyze the passage evidence regarding system constraints
The text explicitly states: 'the operational duration of a closed-circuit system is constrained primarily by the chemical exhaustion of the carbon dioxide absorbent rather than the volume of the gas cylinder.'
Supported inferences must rest strictly on textual statements and valid logical deductions.
2
Evaluate the paraphrase in the valid conclusion
Matching 'operational duration' to 'operational time limit' and 'chemical exhaustion of the carbon dioxide absorbent' to 'capacity of the chemical scrubber' confirms a direct, valid inference.
Proper reading comprehension recognizes accurate paraphrasing without altering the original factual meaning.
3
Filter out unsupported inferences and common distractor traps
Options introducing outside military facts, inverted sequence steps, or absolute claims of zero depletion risk lack textual backing.
Eliminating unsupported assumptions and external knowledge guarantees distinguishing valid inferences.

Key Concept

Distinguishing Supported and Unsupported Inferences
Estimated Time:1m 30s
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Distinguishing Supported and Unsupported Inferences

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