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
Most common organism causing laryngotracheobronchitis is 
Select and explain. 
A. RSV, B. Para-influenza virus, C. Influenza virus, D. H. Influenza
B: Para-influenza virus
Answer: B: Para-influenza virus 
Explanation: Para-influenza virus I and II is the most common organism causing laryngotracheobronchitis. Ref: Textbook of diseases of ENT, PL Dhingra, 7th edition, pg no. 328