Question

Difficulty: MediumSelecting Concluding Sentences and Transitions

Passage

In 1965, chemist Stephanie Kwolek was analyzing synthetic fiber chains at DuPont in search of a lightweight material to reinforce car tires. During her experiments, she generated a strange, cloudy solution that looked unlike the thick, clear polymers she typically worked with. Rather than discarding the unusual mixture, Kwolek convinced a colleague to run it through a spinneret, a machine used to draw liquid polymers into fibers. The resulting fiber was astonishingly strong—five times stronger than steel on a pound-for-pound basis—and resistant to both heat and corrosion. [1]

DuPont quickly recognized the commercial potential of this new material, trademarking it as Kevlar. In the decades following Kwolek's discovery, Kevlar found applications in racing sails, bicycle tires, and optical fiber cables. Most notably, its high tensile strength and lightweight nature revolutionized personal armor, saving the lives of countless military personnel and law enforcement officers.

Question

The writer wants to add a sentence at the end of the first paragraph (at point [1]) to conclude the discussion of Kwolek’s laboratory discovery and transition to the next paragraph's focus on Kevlar's commercial applications. Which of the following sentences best accomplishes this goal?

  1. A
    For example, Kwolek, who was born in Pennsylvania, had always been interested in chemistry from a young age.
  2. B
    Therefore, the resulting substance was exceptionally strong, it was immediately put into mass production by the company.
  3. This breakthrough laboratory experiment laid the foundation for a material that would soon find widespread utility in various industries.Answer
  4. D
    Furthermore, Kwolek wins several prestigious awards for her discovery in the following decades, which remains her most famous achievement.

Answer

The sentence that describes the laboratory experiment laying the foundation for a material that would find widespread utility in various industries is the correct choice.
The correct option effectively concludes the first paragraph's focus on Stephanie Kwolek's laboratory discovery while transitioning to the second paragraph's focus on Kevlar's commercial applications. By stating that the experiment laid the foundation for widespread utility in various industries, it connects the scientific breakthrough with its subsequent practical uses.

Step-by-Step Solution

1
Analyze the purpose of the sentence to be inserted.
The sentence must conclude the first paragraph (laboratory discovery) and transition to the second paragraph (commercial applications).
An effective conclusion-transition sentence must bridge the two paragraphs' main ideas logically.
2
Evaluate the options for structural cohesion and relevance.
The correct choice must connect the laboratory breakthrough to industrial applications without introducing unrelated facts.
Sentences introducing Kwolek's childhood or award history distract from the passage's flow.
3
Check for grammatical correctness in the remaining options.
The option with a comma splice is grammatically incorrect, and the option with present-tense verbs shifts tenses inappropriately.
ACT English questions require sentences to be both rhetorically effective and grammatically correct.

Key Concept

Selecting Concluding Sentences and Transitions
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