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
All are dihydrofolate reductase antagonists, EXCEPT- 
Select and explain. 
A. Methotrexate, B. Cytosine arabinoside, C. Pentamidine, D. Pyrimethamine
B: Cytosine arabinoside
Answer: B: Cytosine arabinoside 
Explanation: Ans. is 'b' i.e., Cytosine Arabinoside Dihydrofolate reductase antagonists are o Methotreyate o Pentamidine o Trimethoprim o Pyrimetham ne