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 of the following is an antimetabolite? \nSelect and explain. \nA. Methotrexate, B. Cyclosporine, C. Etoposide, D. Vinblastine', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Methotrexate is an antimetabolite that acts by inhibiting DHFRase.', 'role': 'assistant'}]