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': "Which one of the following drug is used in Alzheimer's disease : \nSelect and explain. \nA. Tacrine, B. Pemoline, C. Doxapram, D. Methylphenidate", 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]