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
[{'content': 'Allopurinol prevents conversion of : a) Hypoxanthine to xanthine b) Xanthine to hypoxanthine c) Hypoxanthine to I.M.P. d) Xanthine to uric acid \nSelect and explain. \nA. ab, B. cd, C. ad, D. bd', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Xanthine oxidase catalyses the conversion of hypoxanthine to\xa0xanthine as well as xanthine to uric acid. This enzyme is inhibited by allopurinol.', 'role': 'assistant'}]