OG6 阅读 Q27

Choice D is the best answer. In the passage Theis surmises that honey bees were likely repelled not by the enhanced fragrance of the dimethoxybenzene-treated flowers but "by the abundance of beetles"(lines 71-72,"repelled...beetles") found on them. She was able to make that assumption because the honey bees were able to choose between both normal flowers and fragrance-enhanced flowers without any beetles on them, because one of the parameters of the research was that "every half hour throughout the experiments, the team plucked all the beetles off of half the fragrance-enhanced flowers and half the control flowers, allowing bees to respond to the blossoms with and without interference by beetles" (lines 45-50,"So every...beetles"). 
Choice A is incorrect because the passage states only that the scientists observed the bees and beetles on the flowers as soon as they opened (lines 59-61,"We...open"), not both before and after they opened. Choice B is incorrect because although the passage does state that the experiment only took place during the "August flowering season" (line 35,"throughout...season"), it doesn't state that this was a variable in the experiment or had any effect on it. Choice C is incorrect because comparing gourds based on the type of pollination is not related to the issue of what repelled bees from the fragrance-enhanced plants.