OG6 阅读 Q31

Choice B is the best answer. Theis and Adler's research clearly provided an answer to the question of why there is an upper limit on the intensity of the aroma emitted by Texas gourd plants, as their experiment was described as being able to "provide a reason that Texas gourd plants never evolved to produce a stronger scent" (lines 85-86,"The...scent"). 
Choice A is incorrect because Theis and Adler's research was not able to show how to increase pollinator visits to the Texas gourd vine, as the results of their experiment showed that "pollinators, to their surprise, did not prefer the highly scented flowers" (lines 67-68,"Pollinators...indifferent"). Choice C is incorrect because Theis and Adler's research was not able to explain how hand pollination rescued fruit weight, a finding the passage describes as "a hard-to-interpret result" (line 83,"weight...that"). Choice D is incorrect because the passage never indicates that the flowers stop producing fragrance when beetles are present.