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: Pathology
[{'content': 'Which is the most common site for peptic ulcer disease ? \nSelect and explain. \nA. Second portion of Duodenum, B. Proximal stomach, C. Distal stomach, D. First portion of duodenum', 'role': 'user'}, {'content': 'Answer: D \nExplanation: First portion of duodenum is the most common site for PUD.', 'role': 'assistant'}]