This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Larynx, Subject name: ENT
Steeple sign is seen in 
Select and explain. 
A. Croup, B. Acute epiglottitis, C. Laryngomalacia, D. Quinsy
A: Croup
Answer: A: Croup 
Explanation: Acute laryngotracheobronchitis or croup is a viral infection caused by parainfluenza type 1, 2, and sometimes 3. The critical area involved is subglottic larynx producing oedema with stridor and respiratory distress. X-ray (PA view) larynx shows typical "steeple sign" but X-rays are avoided as any manipulation may precipitate acute obstruction. Ref: PL Dhingra 7th edition of Ear, Nose and Throat; Pg no 328