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': 'Opioid analgesic used in treatment of cough is ? \nSelect and explain. \nA. Loperamide, B. Diphenoxylate, C. Codeine, D. Meperidine', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]