You are answering a USMLE-style medical question. Question: A 68-year-old man comes to the physician with a 1-week history of painless hematuria. A CT scan of the urinary tract shows areas of bladder wall thickening. Cystoscopy shows several sessile masses with central necrosis arising from the bladder wall. A biopsy specimen of the bladder masses shows moderately differentiated urothelial cells with abundant mitotic figures and nuclear atypia. The patient most likely has a history of exposure to which of the following? Options: A) Ionizing radiation B) Aromatic amines C) Aflatoxins D) Radon Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.