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
Onion skin appearance is seen in: 
Select and explain. 
A. Chronic osteomyelitis, B. Chronic osteomyelitis with proliferative periostitis, C. Garre’s chronic non-suppurative sclerosing osteitis, D. Both 2 and 3
D: Both 2 and 3
Answer: D: Both 2 and 3 
Explanation: Radiographic picture—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.