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
Laryngotracheobronchitis is caused most commonly by: 
Select and explain. 
A. Adenovirus, B. Parainfluenza virus, C. Rhinovirus, D. None of the above
B: Parainfluenza virus
Answer: B: Parainfluenza virus 
Explanation: Laryngotracheobronchitis is the most common infectious cause of airway obstruction in children, usually occurring between the ages of 6 months and 3 years. It is a viral infection most commonly caused by the parainfluenza virus, although numerous other organisms have been repoed.