Explanation
Correct answer: A.
Choice A is the best answer. The sentence specifies why historians believe Abele designed most of Duke’s campus buildings, noting that most of the buildings feature architectural styles that Abele had studied.
Why the other choices are wrong
Choice B
Choice B is incorrect. While the sentence explains that historians believe Abele designed most of Duke’s campus buildings, it doesn’t specify why historians hold that belief.
Choice C
Choice C is incorrect because the sentence emphasizes the architectural styles of Duke’s campus buildings; it doesn’t specify why historians believe Abele designed the buildings.
Choice D
Choice D is incorrect. While the sentence explains that Abele is believed to have designed most of the buildings on Duke’s campus, it doesn’t specify why historians believe that he designed the buildings.