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: Medicine
[{'content': 'In angina pectoris-during exertion: \nSelect and explain. \nA. Always associated with loss of consciousness, B. Readily responds to oral nitroglycerin, C. Best treated by intravenous morphine, D. Administration of CO2 hastens recovery', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]