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Difficulty: MediumPart-to-Whole Rhetorical Function

In the early twentieth century, astronomers struggled to determine the distance to remote nebulae, with many arguing that these structures resided within our own Milky Way galaxy. To resolve this debate, Edwin Hubble identified Cepheid variables—stars whose periodic fluctuations in luminosity are directly related to their intrinsic brightness—within the Andromeda Nebula. By applying Henrietta Swan Leavitt's period-luminosity relation to these stars, Hubble calculated that Andromeda was located roughly 900,000 light-years away. This measurement far exceeded the estimated size of the Milky Way, conclusively proving that Andromeda was a distinct galaxy. Consequently, Hubble's findings fundamentally expanded the known boundaries of the universe.

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

  1. It describes the specific application of a scientific method that provided the data necessary to resolve the astronomical debate introduced in the text.Answer
  2. B
    It outlines the general historical consensus among twentieth-century astronomers regarding the boundaries of the Milky Way.
  3. C
    It asserts the primary conclusion of the passage concerning the modern scientific understanding of the universe's expansion.
  4. D
    It presents an alternative theory that challenges the validity of Henrietta Swan Leavitt's period-luminosity relation.

Answer

It describes the specific application of a scientific method that provided the data necessary to resolve the astronomical debate introduced in the text.
The correct choice describes the specific application of a scientific method (Hubble applying Henrietta Swan Leavitt's period-luminosity relation) that produced the empirical distance measurement (900,000 light-years) needed to prove Andromeda was a distinct galaxy, thereby resolving the cosmological debate introduced in the opening sentences.

Step-by-Step Solution

1
Identify the main idea and structure of the passage.
The passage outlines a debate about whether nebulae are inside or outside the Milky Way, and explains how Hubble sought to resolve this using Cepheid variables.
Understanding the context allows the reader to place the underlined sentence in the overall flow of the argument.
2
Analyze the specific function of the underlined sentence.
The underlined sentence describes Hubble applying Henrietta Swan Leavitt's period-luminosity relation to calculate the distance of Andromeda.
This establishes the precise methodology and measurement that Hubble generated.
3
Determine how this sentence relates to the text as a whole.
The calculation (900,000 light-years) showed that Andromeda is outside the Milky Way, proving it is a separate galaxy and resolving the initial debate.
The sentence provides the specific empirical data that allows the transition from the problem (the debate) to the resolution (proving Andromeda is a separate galaxy).

Key Concept

Part-to-Whole Rhetorical Function
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Topics

Part-to-Whole Rhetorical Function

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