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Zorluk: OrtaEstablishing Introductions and Thesis Statements

The following is an excerpt from an essay about the history of astronomy.

In the early twentieth century, the Harvard College Observatory employed a group of women, colloquially known as the "Harvard Computers," to analyze astronomical data on photographic plates. Among them was Henrietta Swan Leavitt, whose study of Cepheid variable stars would fundamentally alter our understanding of the universe.

[1] __________________________________________________ Prior to her discovery, astronomers had no reliable way to measure the distance to faraway stars, leaving the scale of the cosmos a subject of intense debate. By establishing that a star's brightness was directly related to its pulsation period, Leavitt provided the essential tool that Edwin Hubble later used to prove that galaxies exist beyond our own.

Which choice most effectively introduces the paragraph by establishing its main focus?

  1. A
    Because she spent years analyzing photographic plates at the observatory to find stellar patterns.
  2. Leavitt discovered a mathematical relationship between the luminosity and the pulsation period of Cepheid variables.Cevap
  3. C
    Leavitt examined thousands of stars; discovering a pattern that would change astronomy.
  4. D
    Although she made important contributions, the compensation for her efforts were only thirty cents an hour.

Cevap

Leavitt discovered a mathematical relationship between the luminosity and the pulsation period of Cepheid variables.
The correct choice must establish a clear introduction to the paragraph's main focus. The option that describes Leavitt discovering a mathematical relationship between the luminosity and pulsation period of Cepheid variables is grammatically correct and directly sets up the main topic of the paragraph. It also provides the necessary antecedent for the phrase 'her discovery' in the following sentence, which explains how astronomers measured distances to stars.

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1
Read the paragraph and analyze the sentence immediately following the blank to identify what information is introduced.
The subsequent sentence mentions 'Prior to her discovery, astronomers had no reliable way to measure the distance to faraway stars,' indicating that the blank must introduce a scientific discovery related to stellar measurement.
To establish a coherent introduction, the missing sentence must provide a logical transition and direct context for the details that follow it.
2
Evaluate each answer choice for grammatical correctness and relevance to the paragraph's main focus.
The option describing Leavitt's discovery of a mathematical relationship is grammatically correct and contextually appropriate. The option starting with 'Because' is a fragment. The option using a semicolon before a participle is a punctuation error. The option with 'compensation... were' contains a subject-verb agreement error and is off-topic.
ACT English questions require sentences to be both grammatically correct and rhetorically effective.

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Establishing Introductions and Thesis Statements
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