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': 'The antianginal effect of propranolol may be attributed to which of the following ? \nSelect and explain. \nA. Block of exercise induced tachycardia, B. Dilation of constricted coronary vessels, C. Increased cardiac force, D. Increased resting heart rate', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]