Spoiler alert: The answer is below the line.
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The right answer is D. Coneflowers, and how many types there are, are not mentioned anywhere else in this paragraph or the entire passage. The passage is about prairies, not specific types of flowers. Therefore, this sentence would distract from the main idea.
The right answer is NOT A because there’s no indication that it’s important for readers to know that the passage is set in the Midwest, and even if it were, the first sentence mentions Illinois, so we already know this.
The right answer is NOT B because the main idea of the paragraph has nothing to do with Iowa coneflowers—it is about Illinois prairies.
The right answer is NOT C because whether coneflowers grow in every state is unrelated to whether the sentence belongs here or not. Why would that matter?