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Difficulty: EasyExplicit Main Idea

Passage:
Flameless ration heaters provide military personnel with a safe and reliable method for heating field rations without producing an open flame. Inside each heater pouch, a chemical reaction occurs when water is added to a mixture of magnesium and iron powder. This reaction produces significant exothermic heat in less than twelve minutes, allowing combat rations to reach optimal serving temperatures in tactical environments where fires are prohibited. By eliminating visible smoke and light, these chemical heaters ensure soldiers receive hot meals without compromising their field positions.

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

  1. A
    Adding water to a mixture of magnesium and iron powder generates exothermic heat.
  2. Flameless ration heaters allow soldiers to heat field rations safely without creating an open flame.Answer
  3. C
    Chemical heating pouches require twelve minutes to reach optimal serving temperatures.
  4. D
    Soldiers must avoid producing smoke and light during all tactical field operations.

Answer

Flameless ration heaters allow soldiers to heat field rations safely without creating an open flame.
The correct statement directly reflects the explicitly stated topic sentence at the start of the passage, which establishes that flameless ration heaters offer a safe and reliable method for heating food without an open flame. The remaining sentences in the paragraph merely provide supporting details regarding the chemical ingredients, heating duration, and tactical advantages of eliminating smoke and light.

Step-by-Step Solution

1
Locate the explicit topic sentence in the passage.
The opening sentence explicitly asserts that flameless ration heaters give military personnel a safe, reliable way to heat meals without an open flame.
Expository paragraphs frequently introduce the overarching central idea directly in the initial sentence.
2
Evaluate remaining sentences to confirm they serve as supporting details.
The sentences discussing the chemical reaction, time requirement, and smoke elimination all explain how the heater achieves flame-free operation.
Supporting details provide evidence and technical explanation for the main claim rather than defining a new topic.
3
Identify the option that captures the primary assertion of the passage.
The statement expressing that flameless ration heaters safely warm field meals without open flames directly reflects the lead sentence.
The correct explicit main idea accurately represents the text's primary thesis without narrowing into isolated facts or broadening excessively.

Key Concept

Explicit Main Idea Identification
Estimated Time:45s
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Explicit Main Idea

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