This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: G.I.T., Subject name: Radiology
[{'content': 'Windsock appearance on barium is seen in? \nSelect and explain. \nA. Duodenal perforation, B. Duodenal ulcer, C. Brunner gland hyperplasia, D. Internal duodenal diverticulum', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ans DWindsock appearanceQ is intraduodenal barium contrast- filled sac that is surrounded by a narrow lucent line seen in intraduodenal diverticulumQ.', 'role': 'assistant'}]