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': 'Which of the following organ is usually the first site of metastasis in a case of osteosarcoma of young female? \nSelect and explain. \nA. Kidneys, B. Lungs, C. Liver, D. CNS', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Lung is the earliest site for metastasis in osteosarcoma. A chest X-ray should be done to detect the same. CT scan may be required in cases where the metastatic lesion is unclear on chest X-ray. Reference: Maheshwari; Essential Ohopaedics; Page no: 240', 'role': 'assistant'}]