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
Thumb sign is seen in? 
Select and explain. 
A. Acute epiglottitis, B. Acute Laryngotracheobronchitis, C. Acute tonsillitis, D. laryngitis
A: Acute epiglottitis
Answer: A: Acute epiglottitis 
Explanation: None