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
Which of the following is an antimetabolite? 
Select and explain. 
A. Methotrexate, B. Cyclosporine, C. Etoposide, D. Vinblastine
A: Methotrexate
Answer: A: Methotrexate 
Explanation: Methotrexate is an antimetabolite that acts by inhibiting DHFRase.