This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Ohopedics Oncology, Subject name: Orthopaedics
[{'content': 'Most common site of Osteogenic sarcoma is: \nSelect and explain. \nA. Femur, upper end, B. Femur, lower end, C. Tibia, upper, D. Tibia, lower end', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Osteosarcoma and GCT involves lower end of femur commonly', 'role': 'assistant'}]