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': 'All of the following are actions of muscarinic antagonists except: \nSelect and explain. \nA. Decreases gastric secretion, B. Prolongs A–V conduction, C. Decreases tracheobronchial secretions, D. Causes contraction of sphincter pupillae', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]