Choice A is the best answer. The first six paragraphs (lines 1-64,"Texas...saw") of the passage introduce a plant (the Texas gourd vine) and its problem (luring enough insects to pollinate it but not too many of those that will harm it) and then describe a study undertaken to deal with "the specific problem of the Texas gourd—how to attract enough pollinators but not too many beetles" (lines 18-20,"took...beetles"). After the specifics of that experiment are described in detail, the results are explained and summarized in the seventh and eighth paragraphs (lines 65-84,"What...development"): "What they saw was double the normal number of beetles...Squash bees were indifferent, and honey bees visited enhanced flowers less often. . . . That added up to less reproduction for fragrance-enhanced flowers” (lines 65-76,"What...flowers").
Choice B is incorrect because Theis and Adler's hypothesis (that more fragrance would make the flowers "even more appealing to bees," line 27,"be...bees") is found in the third paragraph (lines 26-40,"be...fragrance"). Choice C is incorrect because Theis and Adler's methods are described in the third through sixth paragraphs (lines 26-64,"Intuition...saw"), not the seventh and eighth (lines 65-84,"What...development"). Choice D is incorrect because the seventh and eighth paragraphs detail the results in an experiment but do not focus on the researchers' reasoning.