This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: CHF, Angina Pectoris and Myocardial Infarction, Subject name: Pharmacology
[{'content': 'Propanolol is contraindicated in a patient of angina pectoris who is already receiving: \nSelect and explain. \nA. Nifedipine, B. Aspirin, C. Verapamil, D. Isosorbide mononitrate', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Propanolol is a b-blocker. Verapamil should not be given with b blockers because additive sinus depression, conduction defects or asystole may occur.', 'role': 'assistant'}]