There is no consensus among researchers regarding what qualifies a substance as a pheromone. While most agree on a basic definition of pheromones as chemicals released by one individual of a species which, when detected by another individual of the same species, elicit a specific behavioral or physiological response, some researchers also specify (10) that the response to pheromones must be unconscious. In addition, the distinction between pheromones and odorants— chemicals that are consciously detected as odors---can be blurry, and some researchers classify pheromones as a type of odorant. Evidence that pheromone responses may not involve conscious odor perception comes from the finding that in many species, pheromones are processed by the vomeronasal (or accessory olfactory) system, which uses a special structure in the nose, the vomeronasal organ (VNO), to receive chemical signals. The neural connections between the VNO and the brain are separate from those of the main olfactory system, whose processing of odorants triggers sensations of smell. But while the VNO does process many animal pheromone signals, not all animal pheromones work through the VNO. Conversely, not all chemical signals transmitted via the VNO qualifyas pheromones. For example, garter snakes detect a chemical signal from earthworms—one of their favorite foods—via
the VNO, and they use this signal to track their prey.
The primary purpose of the passage is to
原文第一句”There is no consensus among researchers regarding what qualifies a substance as a pheromone.“应该是中心句。所以文章主要是说对于pheromone的分类大家一直有分歧”，后面的正文也是举了几个例子，说明pheromone和odorants之间容易混淆，以及通过VNO来分类也会造成分歧，等等。
C是”提出了关于pheromone组成成分（what constitutes a pheromone），和所说的定义混淆无关。
2018-03-21 20:27:43 回复
【OG19-P384-444题】The idea that carotenoid-based coloration is significant partly because carotenoids are required for health suggests that a lack of bright coloration in a male is most likely to indicate which of the following?