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': 'You decide not to prescribe sildenafil in a patient because the patient told you that he is taking an antianginal drug. Which of the following can it be ? \nSelect and explain. \nA. Calcium channel blockers, B. β adrenergic blockers, C. Organic nitrates, D. Angiotensin converting enzyme inhibitors', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]