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Difficulty: MediumPart-to-Whole Rhetorical Function

The search for life on Mars has long focused on the detection of methane (CH4CH_4), a gas frequently associated with biological activity on Earth. In 20182018, NASA's Curiosity rover detected a seasonal spike in atmospheric methane, sparking intense debate among planetary scientists. While some researchers immediately posited that this fluctuation was evidence of microbial methanogenesis beneath the Martian surface, others urged caution, noting that abiotic processes could produce identical signatures. Specifically, reactions between water (H2OH_2O) and olivine-rich rocks—a process known as serpentinization—can release methane under Martian conditions. Consequently, confirming the origin of Martian methane requires analyzing the carbon isotopes within the gas, rather than merely measuring its concentration.

Which choice best describes the function of the underlined sentence in the text as a whole?

  1. A
    It establishes the main argument of the passage by demonstrating that abiotic reactions are the primary source of Martian gases.
  2. B
    It dismisses the possibility of microbial life on Mars by proving that serpentinization is the sole cause of atmospheric methane.
  3. It presents conflicting scientific interpretations of a recent finding, setting up the passage's discussion of how to resolve this ambiguity.Answer
  4. D
    It states the passage's final conclusion about the most reliable method for identifying biological activity on Mars.

Answer

The correct answer is the option stating that the underlined sentence presents conflicting scientific interpretations of a recent finding, setting up the passage's discussion of how to resolve this ambiguity.
The passage begins by noting the detection of a seasonal spike in Martian methane, which has led to disagreement among scientists. The underlined sentence introduces this disagreement by explaining that some scientists view the spike as evidence of microbial life while others believe it could have an abiotic origin. The subsequent sentences elaborate on this second possibility (serpentinization) and explain how scientists can resolve the dispute (isotope analysis). Therefore, the underlined sentence functions to present conflicting interpretations of a finding to set up a discussion of how to determine which interpretation is correct.

Step-by-Step Solution

1
Analyze the underlined sentence to identify its immediate meaning and context.
The sentence describes a division among scientists: some believe a methane spike indicates microbial life, while others suggest it could be caused by abiotic processes.
To establish what role this specific part plays in the text before examining its relationship to the surrounding sentences.
2
Examine the sentences that follow the underlined portion.
The subsequent sentences explain one specific abiotic process (serpentinization) and suggest a method (isotope analysis) to determine whether the methane is biological or abiotic in origin.
To see how the rest of the passage builds on the ideas introduced in the underlined sentence.
3
Compare the function of the underlined sentence to the options to find the best match.
The option stating that the sentence presents conflicting interpretations of a recent finding to set up a discussion on how to resolve the ambiguity matches perfectly.
To identify the correct rhetorical relationship between the part and the whole text.

Key Concept

Identifying the rhetorical function of a specific sentence within the context of a short academic passage.
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Topics

Part-to-Whole Rhetorical Function

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