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Difficulty: MediumOverall Text Structure Analysis

For years, marine biologists debated the primary function of the narwhal’s elongated tusk, with early hypotheses suggesting it was used exclusively as a weapon for defense. However, recent drone footage has challenged this assumption by showing narwhals using their tusks to tap and stun small fish. Furthermore, anatomical analyses reveal that the tusk is actually a highly sensitive sensory organ containing millions of nerve endings, allowing the animal to detect changes in water salinity and temperature. Consequently, researchers now believe that the tusk serves a dual purpose, functioning both as a tactile tool for foraging and as an environmental sensor.

Which choice best describes the overall structure of the text?

  1. It introduces a traditional hypothesis about a physical trait, presents observation-based evidence that challenges this view, details anatomical findings that reveal a different function, and summarizes a modern consensus that combines both roles.Answer
  2. B
    It outlines a scientific methodology for studying marine animals, identifies several limitations of that methodology, proposes a new technological tool, and predicts how that tool will resolve a debate.
  3. C
    It defends the claim that narwhals use their tusks solely for combat, refutes evidence from recent drone studies, lists the chemical properties of the tusk, and calls for more funding for underwater research.
  4. D
    It compares the sensory capabilities of narwhals with those of other marine mammals, discusses the evolutionary history of tusks, and argues that most mammalian tusks are primarily used to monitor water temperature.

Answer

It introduces a traditional hypothesis about a physical trait, presents observation-based evidence that challenges this view, details anatomical findings that reveal a different function, and summarizes a modern consensus that combines both roles.
The correct option accurately describes the sequence of rhetorical moves in the passage. The text starts by introducing a traditional hypothesis (that the narwhal's tusk was used exclusively for defense), presents observation-based evidence that challenges this assumption (drone footage showing tusks used for foraging), details anatomical findings that point to a different function (the presence of sensory nerve endings), and concludes by outlining a modern consensus that integrates both of these newly discovered roles.

Step-by-Step Solution

1
Analyze the first sentence of the passage to identify the starting point.
The passage begins by presenting a traditional view/hypothesis: the idea that the narwhal's tusk was used exclusively for defense.
This establishes the initial context and the hypothesis being examined.
2
Analyze the transition in the second and third sentences.
The word 'However' introduces new drone observations showing a different behavior (stunning fish), and the third sentence adds anatomical findings showing the tusk is a sensory organ.
These sentences introduce new evidence that challenges and expands upon the initial hypothesis.
3
Analyze the final sentence to identify how the text concludes.
The passage concludes by showing that researchers now believe the tusk serves a dual purpose, integrating both foraging and sensory functions.
This represents a modern scientific consensus that synthesizes the different findings.

Key Concept

Overall Text Structure Analysis
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Topics

Overall Text Structure Analysis

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