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Difficulty: EasyExplicit Main Idea

Thermal imaging cameras have become an indispensable tool for shipboard firefighting teams. These handheld devices allow firefighters to locate the seat of a fire through dense smoke that completely blocks visible light. In addition, thermal cameras can detect hot spots hidden behind bulkheads before flames spread to adjacent compartments. By displaying infrared radiation as a visible image, the technology also enables rescue teams to quickly find trapped personnel in zero-visibility conditions.

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

  1. A
    Thermal cameras are used solely to locate hot spots hidden behind bulkheads.
  2. Thermal imaging cameras are an essential tool for shipboard firefighting operations.Answer
  3. C
    Dense smoke completely blocks visible light during shipboard fires.
  4. D
    All naval vessels require automated infrared fire suppression systems.

Answer

Thermal imaging cameras are an essential tool for shipboard firefighting operations.
The correct answer directly restates the explicit main idea presented in the opening sentence of the paragraph: thermal imaging cameras are indispensable (essential) for shipboard firefighting teams. Every other sentence in the passage provides supporting evidence explaining how and why these cameras are essential.

Step-by-Step Solution

1
Identify the topic sentence that states the central claim of the passage.
The first sentence explicitly states that thermal imaging cameras are an indispensable tool for shipboard firefighting teams.
Explicit main ideas are directly stated in an identifiable sentence, often at the beginning of the paragraph.
2
Verify that subsequent sentences provide supporting details for this central claim.
The remaining sentences detail specific uses of the cameras: finding the source of a fire, checking behind bulkheads, and locating personnel.
A valid main idea must encompass all supporting examples rather than focusing on just one function.
3
Select the option that accurately paraphrases the explicit topic sentence.
The option stating that thermal imaging cameras are an essential tool for shipboard firefighting operations matches the topic sentence.
Paraphrasing the opening claim confirms comprehension of the overall paragraph.

Key Concept

Identifying an explicitly stated main idea in an introductory topic sentence
Estimated Time:45s
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Topics

Explicit Main Idea

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