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': 'Osteomyelitis begins as an inflammation of \nSelect and explain. \nA. Cortical bone, B. Periosteum, C. Medullary bone, D. Periosteum and inner cortex', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]