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: Surgery
[{'content': 'Following is least common about angiodyplasia of colon - \nSelect and explain. \nA. Involvement of cecum, B. Involvement of rectum in 50% of cases, C. Affecting age group > 40 yrs., D. Cause of troublesome lower G.I. hemorrhage', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]