This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pharmacology
[{'content': 'Buprenorphine acts by following mechanism \nSelect and explain. \nA. Mu receptor antagonist, B. Kappa receptor antagonist, C. Mu receptor partial agonist, D. Kappa receptor partial agonist', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]