This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Skeletal system, Subject name: Radiology
[{'content': "Codman's triangle is a feature of - \nSelect and explain. \nA. Osteosarcoma, B. Osteochondroma, C. Osteoid osteoma, D. Chondrosarcoma", 'role': 'user'}, {'content': 'Answer: A \nExplanation: A Codman triangle develops when a poion of periosteum is lifted off of the coex by tumor, pus, or hemorrhage at a leading edge . This aggressive form of periosteal reaction is commonly seen in osteosarcomas and occasionally with infection and metastases.', 'role': 'assistant'}]