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: Surgery
[{'content': 'Drug of choice for renal colic - \nSelect and explain. \nA. Methadone, B. Pentazocine, C. Voveran, D. Piroxican', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]