Answer: C) counterfeit : authentic
Explanation: an analogy is a comparison between one thing and another, usually with the purpose of explanation or clarification, this comparison is based on one similarity or difference between specific features of two things. The relationship between the given pair of words "incompetent" and "adequate" is that they are antonyms, from the given options, the other pair of words that has that relationship, is the corresponding to option C: counterfeit and authentic, they are also antonyms.