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
Methotrexate is what class of anti cancer drug ? 
Select and explain. 
A. Alkylating agents, B. Antimetabolites, C. Microtubule damaging agents, D. Topoisomerase inhibitors
B: Antimetabolites
Answer: B: Antimetabolites 
Explanation: Ans. is 'b' i.e., Antimetabolites