You are answering a USMLE-style medical question. Question: A 56-year-old man comes to the physician because of a 1-day history of sudden severe pain in his right great toe. Four months ago, he had an episode of severe joint pain involving his left knee that lasted several days and resolved with over-the-counter analgesics. He has a history of hypertension treated with hydrochlorothiazide and nephrolithiasis. Examination shows erythema, swelling, warmth, and tenderness of the right metatarsophalangeal joint; range of movement is limited by pain. His serum uric acid is 12 mg/dL. Arthrocentesis yields cloudy fluid with a leukocyte count of 18,500/mm3 (80% segmented neutrophils). Polarized light microscopy of the synovial fluid is shown. Which of the following is the mechanism of action of the most appropriate long-term pharmacotherapy for this patient's condition? Options: A) Increased conversion of uric acid to allantoin B) Inhibition of phospholipase A C) Inhibition of xanthine oxidase D) Increased renal excretion of urate Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.