This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Anti-Neoplastic Agents, Subject name: Pharmacology
Which is an antimetabolite 
Select and explain. 
A. Cyclosporine, B. Methotrexate, C. Etoposide, D. Vinblastine
B: Methotrexate
Answer: B: Methotrexate 
Explanation: Ans. is 'b' i.e. Methotrexate AntimetabolitesThese are synthetic analogues of normal metabolites related to components of DNA or of coenzymes involved in nucleic acid synthesis.They act by Competition i.e. they "deceive" or "defraud" bodily processes.Instead of the natural substrate they get themselves incorporated, forming dysfunctional molecules.These drugs act on the S phase of the cell cycle, thus only dividing cells are responsiveFolic acid analoguesPurine antagonistsPyrimidine antagonistst Methotrexate* 6 mercaptopurine* S fluorouracil* Pemetrexed* 6thioguanine* Cytarabine