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
An antimetabolite which undergoes biotransformation to form an inhibitor of DNA polymerase is - 
Select and explain. 
A. Vinablastine, B. Cytosine arabinoside, C. Methotrexate, D. Chlorambucil
B: Cytosine arabinoside
Answer: B: Cytosine arabinoside 
Explanation: Ans. is 'b' i.e., Cytosine arabinosideo Cytarabine is phosphorylated in the body to the corresponding nucleotide which inhibits DNA synthesis by inhibiting DNA polymerase.