This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Tumors, Subject name: Orthopaedics
[{'content': "Sun-ray appearance is characteristic of \nSelect and explain. \nA. Osteoclastoma, B. Osteosarcoma, C. Ewing's sarcoma, D. Osteoid osteoma", 'role': 'user'}, {'content': "Answer: B \nExplanation: Osteosarcoma is the second most common, and a highly malignant primary bone tumour. Sun-ray appearance: In X-ray, as the periosteum is unable to contain the tumour, the tumour grows into the overlying soft tissues. New bone is laid down along the blood vessels within the tumour growing centrifugally, giving rise to a 'sun-ray appearance' on the X-ray. Reference: Maheshwari; Essential Ohopaedics; 9th ed Page no: 240", 'role': 'assistant'}]