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Difficulty: Very hardCausal Detail Extraction

In deep-water naval operations, sonar detection capabilities are profoundly influenced by the ocean's thermal structure. While surface temperature fluctuations typically degrade acoustic signal integrity by scattering high-frequency waves, the presence of a thermocline—a distinct layer where temperature drops rapidly with depth—creates an entirely different phenomenon. Instead of merely scattering, acoustic energy emitted below this boundary is refracted downward due to the increased water density. Consequently, this downward refraction prevents the sound waves from reaching surface receivers, creating an acoustic shadow zone. Paradoxically, while commanders often attribute sudden communication blackouts in these regions to surface scattering, it is actually the abrupt density gradient within the thermocline that effectively cloaks submerged vessels from shallow-draft tracking vessels.

Based on the passage, what effectively causes a submerged vessel to become cloaked from shallow-draft tracking vessels?

  1. An abrupt density gradient within the thermoclineAnswer
  2. B
    The scattering of high-frequency waves by surface temperature fluctuations
  3. C
    An acoustic shadow zone that rapidly decreases the water temperature
  4. D
    The complete absorption of sonar energy by the surrounding deep-water environment

Answer

An abrupt density gradient within the thermocline
The final sentence of the passage explicitly states that 'it is actually the abrupt density gradient within the thermocline that effectively cloaks submerged vessels from shallow-draft tracking vessels.' The text directly identifies this gradient as the cause of the cloaking effect, contrasting it with the incorrect assumption of surface scattering.

Step-by-Step Solution

1
Analyze the question stem to identify the specific effect being queried.
The question asks for the direct cause of a submerged vessel being 'cloaked' from shallow-draft tracking vessels.
Focusing on the exact requested effect ensures the correct causal relationship is extracted from a passage containing multiple causes and effects.
2
Scan the passage for the mention of submerged vessels being cloaked.
The final sentence states: '...it is actually the abrupt density gradient within the thermocline that effectively cloaks submerged vessels from shallow-draft tracking vessels.'
Locating the exact phrasing in the text reveals the explicit cause linked to the target effect.
3
Differentiate the actual cause from the presumed cause mentioned in the same sentence.
The passage notes that commanders mistakenly attribute this cloaking to 'surface scattering', but clarifies the actual cause is the 'abrupt density gradient'.
The passage uses a contrast structure to test the reader's ability to extract the true cause over a commonly assumed or incorrectly attributed one.

Key Concept

Causal Detail Extraction
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Topics

Causal Detail Extraction

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