There is no consensus among researchers regarding what qualifies a

I'm an airhead, and wrote this a few weeks ago when I didn't have internet access... but never posted it. There are lots of great responses here already, but I'll pile on, just in case it's helpful.


We're asked to state the primary purpose. It's not enough to pick a choice that seems factually true. We need to pick the choice that best states the overall reason the author is writing the entire passage. And here's the structure of the passage:

• There's no consensus among researchers regarding what qualifies as a pheremone.
• Some researchers specify that pheremones must be unconsciously detected.
• On the other hand, some researchers classify pheremones as odorants, which means that they must be consciously detected.
• In many species, pheremones are processed by the VNO, which means that pheremones could be odorants but still be unconsciously detected.
• The VNO also processes non-odorant chemicals, which can also trigger a behavioral response without any kind of odor.

This is a funky cloud of smells (and non-smells). The author is presenting one new fact after the next, repeatedly challenging the ways that researchers classify pheromones by bringing up evidence that would contradict those classifications. By the end of the passage, it seems like none of the classifications really work. So rather than leading us to any one definition, the author is writing this passage in order to walk us through all of the ways that researchers attempt to classify pheromones. No wonder there's no consensus over what qualifies as a pheromone.


The author didn't write this entire paragraph just to tell us that the VNO and the main olfactory system are similar but different. Instead, author brings up this evidence to serve a bigger point: that the classifications researchers are using aren't very helpful. Eliminate (A).


The phrase "summarize the debate" is tempting. But like (A), choice (B) focuses too narrowly on the VNO. The passage isn't about the debate over VNO. It's about the debate over pheromone classifications. Eliminate (B).


Exactly! The author is walking us through the various classifications of a pheremone and citing evidence to support (or complicate) each one. (C) matches our understanding of the overall purpose, so we'll keep it around.


The author never proposes a new definition. The author lists multiple definitions proposed by researchers, but doesn't state that any one of them is the one we should accept. At the end of the passage, the author hasn't shown that any of these definitions is satisfactory, and the debate goes on without consensus. That's why we eliminate (D).


Again, this is not why the author is writing the passage as a whole. It's just one of the researcher viewpoints that the author presents in order to lay out all the issues at play in this debate. Eliminate (E).

(C) Is the only good choice available, and it's a fine summary of why the author wrote this passage.

I hope this helps!