This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Chemotherapy, Subject name: Pharmacology
[{'content': "High dose methotrexate is used for the treatment of(REPEAT) \nSelect and explain. \nA. Osteosarcoma, B. Rhabdomyosarcoma, C. Retinoblastoma, D. Ewing's sarcoma", 'role': 'user'}, {'content': "Answer: A \nExplanation: Ref: Harrison's 17th/612 Drugs used for osteosarcoma are: Doxorubicin Ifosfamide Cisplatin High dose methotrexate with leucovorin", 'role': 'assistant'}]