This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Pharmacology
[{'content': 'Which of the following drug is not used for overactive bladder? \nSelect and explain. \nA. Duloxetine, B. Darifenacin, C. Oxybutynin, D. Flavoxate', 'role': 'user'}, {'content': 'Answer: A \nExplanation: .', 'role': 'assistant'}]