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': 'Angiotensin converting enzyme inhibitors are useful in congestive heart failure as: \nSelect and explain. \nA. First choice drugs unless contraindicated, B. An alternative to diuretics, C. A substitute for digitalis, D. Adjuncts only in resistant cases', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]