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': 'In which of the following organs, the effect of atropine on parasympathetic system is of the longest duration ? \nSelect and explain. \nA. Eye, B. Heart, C. Salivary glands, D. Urinary bladder', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]