This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Osteogenic Sarcoma, Subject name: Orthopaedics
[{'content': 'What is the most common site of osteosarcoma: \nSelect and explain. \nA. Lower end of femur, B. Upper end of humerus, C. Lower end of tibia, D. Upper end of femur', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e. lower end of femur * Common sites in decreasing order of frequency:Lower end of femur*Upper end of tibia *Upper end of humerusSome other common sites* Osteoclastoma - lower end of femur** Ewing's -tibia** Ivory osteoma -frontal sinus** Osteoid osteoma -tibia** adamantinoma -mandible** Chordoma -sacrum and cervical spine** Multiple myeloma -vertebra** Enchondroma -small bones of hand and feet** Simple bone cyst -upper end of humerus** Aneurysmal bone cyst -lower end of humerus** Bone secondaries -vertebra** Osteochondroma -metaphysis of femur** Rhabdomyosarcoma -head and neck area*", 'role': 'assistant'}]