This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cardiovascular system, Subject name: Pharmacology
[{'content': 'Anti-arrhythmic drug+ antianginal drugs \nSelect and explain. \nA. Beta blockers, B. Nitrates, C. Rho kinase inhibitor, D. Potassium channel openers', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Beta blockers are class 2 anti arrhythmic agents which are also used in angina except in variant angina. Ref katzung 12th ed.', 'role': 'assistant'}]