The correct answer is C. The suffix -cy is indicating that the word is a noun, so the meaning should be eithef related to a concrete or abstract thing. The only meaning that can be related to an abstract idea is "the state of being false". Choices B and D refer to ideas tipically expressed by adjectives, as they are qualities. Choice A is the opposite meaning of fallacy.
I think it's A, because "very" seems like a weak word, and "nice" also seems like a weak word judging by the sentence. Hope I helped! :D
She doesn’t care about people/ things around her