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
Allopurinol potentiates action of : 
Select and explain. 
A. Azathioprine, B. Busulfan, C. Actinomycin, D. Procarbazine
A: Azathioprine
Answer: A: Azathioprine 
Explanation: None