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': 'What is the drug of choice for CMV (cytomegalovirus) retinitis in patients with AIDS \nSelect and explain. \nA. Acyclovir, B. Ganciclovir, C. Pentamidine, D. Cotrimoxazole', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]