This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Radiology
[{'content': "An eight year old boy presents with back pain and mild fever. His plain X-ray of the dorsolumbar spine reveals a solitary collapsed dorsal vertebra with preserved disc spaces. There was no associated soft tissue shadow. The most likely diagnosis is - \nSelect and explain. \nA. Ewing's sarcoma, B. Tuberculosis, C. Histiocytosis, D. Metastasis", 'role': 'user'}, {'content': 'Answer: C \nExplanation: Solitary collapsed vertebra (vertebra plana) with preserved disc spaces in a child suggests the diagnosis of Eosinophilic granuloma (a type of Histiocytosis).', 'role': 'assistant'}]