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
Drug of choice for Hairy cell leukemia 
Select and explain. 
A. Methotrexate, B. Gemcitabine, C. Cladribine, D. Decitabine
C: Cladribine
Answer: C: Cladribine 
Explanation: Cladribine is a purine analogue, which is  DOC for Hairy cell leukemia.