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Difficulty: MediumCausal Detail Extraction

During wildland firefighting operations, crown fires represent one of the most dangerous fire behaviors. When intense surface fires generate extreme convective heat, the ascending thermal column preheats and dries the moisture out of the elevated tree canopies above. Because the moisture barrier within the needles is eliminated, tree crowns ignite rapidly and allow the fire to spread through the canopy independent of ground vegetation. Consequently, suppression crews must immediately shift from direct ground attack to indirect barrier containment.

According to the passage, what causes tree crowns to ignite rapidly?

  1. A
    The fire spreads through the canopy independent of ground vegetation.
  2. The moisture barrier within the needles is eliminated by convective heat.Answer
  3. C
    Suppression crews shift from direct ground attack to indirect containment.
  4. D
    High ambient wind speeds carry burning embers across established firelines.

Answer

The moisture barrier within the needles is eliminated by convective heat.
The passage explicitly signals the cause using the subordinating conjunction 'Because' in the sentence: 'Because the moisture barrier within the needles is eliminated, tree crowns ignite rapidly.' Therefore, the elimination of needle moisture by convective heat is the stated cause of rapid crown ignition.

Step-by-Step Solution

1
Identify the target effect in the question stem.
The target effect to explain is the rapid ignition of tree crowns.
Establishing the specific event helps locate the direct causal signal in the text.
2
Locate the explicit causal marker in the passage connected to crown ignition.
Found the clause: 'Because the moisture barrier within the needles is eliminated, tree crowns ignite rapidly...'
The transition word 'Because' introduces the direct cause of the subsequent action.
3
Match the identified cause to the correct answer choice.
The elimination of the needle moisture barrier caused by convective heat is the stated reason.
Eliminates distractors that represent subsequent effects, unrelated text fragments, or outside knowledge.

Key Concept

Causal Detail Extraction
Estimated Time:1m 0s
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Topics

Causal Detail Extraction

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