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': 'Onion skin appearance is seen in: \nSelect and explain. \nA. Chronic osteomyelitis, B. Chronic osteomyelitis with proliferative periostitis, C. Garre’s chronic non-suppurative sclerosing osteitis, D. Both 2 and 3', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Radiographic\xa0picture—Classical onion skin appearance due to cortical layer duplication is seen in both chronic osteomyelitis with proliferative periostitis and Garre’s chronic non suppurative sclerosing osteitis.', 'role': 'assistant'}]