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': 'Vasomotor reversal of Dale is due to: \nSelect and explain. \nA. α blocker, B. β–blocker, C. α and β–blocker, D. None', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]