OG6 阅读 Q30

Choice B is the best answer. To be "indifferent" is to be apathetic, or without care or concern. In the context of an experiment that tested whether or not insects preferred normally scented flowers or ones with enhanced fragrance, describing the squash bees as "indifferent" implies they did not care about the scents and were equally drawn to both types of flowers. 
Choice A is incorrect because "indifference" suggests the amount of concern one has about something but not anything to do with physical capabilities (such as being able to distinguish between the flowers). Choice C is incorrect because "indifference" suggests that one has no preference. Choice D is incorrect because the squash bees are said to be "indifferent" to certain flowers based on their fragrance, not on the number of beetles that may or may not be on them.