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: ENT
[{'content': 'Thumb sign is seen in? \nSelect and explain. \nA. Acute epiglottitis, B. Acute Laryngotracheobronchitis, C. Acute tonsillitis, D. laryngitis', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]