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': 'Catecholamine action on α–receptors causes: \nSelect and explain. \nA. Increased atrial contraction, B. Increased heart rate, C. Detrusor relaxation, D. Gastrointestinal sphincter contraction', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]