I had a hard time deciding between (C) and (E). I ended up choosing (E) because it seemed like the author supported the idea more. But I don't see how (C) is necessarily incorrect.
In lines 33-34 the passage states "yet it is not only the pursuit and acquisition of knowledge that makes one a professional."
Doesn't "not only" imply that it is a necessary condition, perhaps just a partial one? So in this sense, I thought it was BOTH the pursuit and acquisition of knowledge and the publicly professed devotion to a way of life.
Or all logic aside, is (C) incorrect because of the phrasing "long and difficult?"