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Difficulty: MediumNegative Detail Identification

Steel ship hulls in saltwater environments are highly vulnerable to galvanic corrosion caused by electrochemical reactions between dissimilar metals. To protect the primary steel structure, sacrificial anodes made of zinc or aluminum alloys are mounted directly to the hull below the waterline. Because zinc has a lower electrochemical potential than steel, the zinc anode oxidizes preferentially, corroding away while the steel hull remains protected as the cathode. Sacrificial anodes require zero external electrical power to function and are routinely inspected during drydock servicing. Technicians schedule replacement when an anode is depleted by approximately 50 percent of its original mass.

According to the passage, all of the following statements regarding sacrificial zinc anodes are true EXCEPT:

  1. A
    They oxidize preferentially to prevent the ship's steel hull from corroding.
  2. They require a continuous supply of external electrical power to function.Answer
  3. C
    They are attached directly to sections of the hull situated below the waterline.
  4. D
    They are scheduled for replacement once roughly 50 percent of their mass has eroded.

Answer

Sacrificial zinc anodes require a continuous supply of external electrical power to function.
The passage explicitly states that sacrificial anodes 'require zero external electrical power to function.' Therefore, claiming that they require a continuous supply of external electrical power directly contradicts the provided text, making it the correct answer to this negative-detail question.

Step-by-Step Solution

1
Analyze the question stem to identify the negative qualifier.
The stem uses the negative qualifier 'EXCEPT', requiring the selection of a statement that is unsupported or directly contradicted by the passage.
Recognizing negative phrasing ensures focus on finding the false statement rather than a true detail.
2
Verify each statement against the factual details provided in the passage.
The text confirms that anodes oxidize preferentially, attach below the waterline, and are replaced at 50 percent depletion, but states they 'require zero external electrical power to function.'
Cross-referencing each claim against the passage eliminates stated facts and isolates the contradictory assertion.
3
Select the contradicted claim as the final answer.
The assertion that sacrificial anodes require a continuous external electrical power supply directly contradicts the text.
Direct contradictions represent the target negative detail in standard reading comprehension assessments.

Key Concept

Identifying details that contradict or are absent from factual technical text under negative question phrasing.
Estimated Time:1m 0s
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Topics

Negative Detail Identification

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