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: Medicine
[{'content': 'All are true about starting of β-blocker therapy in a case of CHF except - \nSelect and explain. \nA. They should be started with optimal doses, B. They should be gradually increased over weeks, C. Special precautions should be taken in cases of NYHA class III and IV, D. Carvedilol and Metoprolol are the preferred drugs', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]