A firefly uses specialized muscles to draw oxygen into its lower abdomen through narrow tubes, triggering a chemical reaction whereby the oxygen combines with chemicals in the firefly’s abdomen to produce a glow. ______blank when the firefly stops drawing in oxygen, the reaction—and the glow—cease.
Which choice completes the text with the most logical transition?
Correct answer: B
Explanation
Choice B is the best answer. “By contrast” logically signals that the information in this sentence—that a firefly’s glow ceases when it stops drawing in oxygen—contrasts with the previous sentence’s discussion of the processes that cause a firefly to begin to glow.
Choice A is incorrect because “for instance” illogically signals that the information in the sentence exemplifies the previous sentence’s discussion of how a firefly begins to glow. Instead, it contrasts with the previous sentence’s discussion. Choice C is incorrect because “specifically” illogically signals that the information in the sentence provides specific details elaborating on the previous sentence’s discussion of how a firefly begins to glow. Instead, it contrasts with the previous sentence’s discussion. Choice D is incorrect because “in conclusion” illogically signals that the information in the sentence sums up the previous sentence’s discussion of how a firefly begins to glow. Instead, it contrasts with the previous sentence’s discussion.
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