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Difficulty: MediumExplicit Main Idea

Submarine atmospheric control systems utilize electrolytic oxygen generators as their primary method to sustain breathable air during extended submerged deployments. In enclosed undersea vessels, ambient oxygen is continuously consumed by the crew while carbon dioxide accumulates. Rather than carrying hazardous reserves of compressed oxygen tanks that occupy vital hull space, the onboard generation unit uses electrical currents to split purified seawater into breathable oxygen gas and byproduct hydrogen, which is safely vented overboard. Consequently, electrolytic oxygen generators provide the essential life-support capability required for submarines to remain submerged for months at a time.

Which of the following statements best expresses the main idea of the passage?

  1. A
    Hydrogen gas produced during electrolysis is safely vented overboard into the sea.
  2. Electrolytic oxygen generators are the vital systems used to sustain breathable air during extended submarine operations.Answer
  3. C
    Compressed oxygen storage tanks present severe safety hazards in enclosed undersea vessels.
  4. D
    Submarine atmospheric control requires eliminating all hazardous gases and managing hull space.

Answer

Electrolytic oxygen generators are the vital systems used to sustain breathable air during extended submarine operations.
The correct answer directly restates the explicit topic sentence found in the first and final sentences of the passage, capturing the central theme that electrolytic oxygen generators provide the primary life-support capability for long-duration submarine missions.

Step-by-Step Solution

1
Locate the explicit topic sentence and concluding synthesis in the passage.
The opening sentence identifies electrolytic oxygen generators as the primary method to sustain breathable air, and the closing sentence reinforces that they provide the essential life-support capability for long deployments.
Explicit main ideas in expository paragraphs are stated directly in the lead or summary sentence.
2
Differentiate the overarching message from supporting facts and contrasts.
Mentions of hydrogen venting, seawater splitting, and compressed tank hazards are secondary details supporting the central point.
A main idea must cover the full scope of the text rather than single supporting steps.

Key Concept

Identifying Explicit Main Idea
Estimated Time:1m 0s
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Explicit Main Idea

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