C is the only right answer. It must be something about the prefix "non" that makes people think the person is not "plussed," but I don't know how anyone got the idea that being "plussed" meant that you were agitated and that adding "non" to it would mean you're just not bothered at all. This is an incredibly common misuse of the word, but it really does indicate confusion, not a blasé attitude. Hit the dictionary if you don't believe me. (Oh, and B and D are just answer choices I made up.)