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
Among the Drugs used in over active bladder, which of the folloeing has minimum CNS Penetration: 
Select and explain. 
A. Trospium., B. Tolterodine., C. Solefenacin., D. Oxybutynin.
A: Trospium.
Answer: A: Trospium. 
Explanation: It has less CNS penetration because of its quaternary ammonium structure.