You are answering a USMLE-style medical question. Question: A 41-year-old man presents to the clinic with the complaints of abdominal discomfort and cramping for the past 4 months. He also mentions that he has grossly bloody stool and most of the time an urge to defecate. He has a history of bulimia with laxative abuse several years ago. He admits having lost about 5 lb in the past month. His temperature is 37° C (98.6° F), respiratory rate is 15/min, pulse is 77/min, and blood pressure is 105/86 mm Hg. On physical examination, a mild conjunctival pallor is evident, and the rectum is erythematous, indurated, and tender. Colonoscopy demonstrates continuous mucosal lesions throughout the rectum to the hepatic flexure of the colon. What is the most likely diagnosis? Options: A) Ulcerative colitis B) Celiac disease C) Irritable bowel syndrome D) Crohn’s disease Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.