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': 'Among the Drugs used in over active bladder, which of the folloeing has minimum CNS Penetration: \nSelect and explain. \nA. Trospium., B. Tolterodine., C. Solefenacin., D. Oxybutynin.', 'role': 'user'}, {'content': 'Answer: A \nExplanation: It has less CNS penetration because of its quaternary ammonium structure.', 'role': 'assistant'}]