This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Small & Large Intestine, Subject name: Surgery
Ulcerative colitis most commonly involves: 
Select and explain. 
A. Rectum, B. Anus, C. Ascending colon, D. Ileum
A: Rectum
Answer: A: Rectum 
Explanation: Ans. (a) RectumRef: Sabiston 20th edition, Page 1339* Most common site of ulcerative colitis: Rectum* Most common site of Crohn's disease: Terminal ileum