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': 'Laryngotracheobronchitis is caused most commonly by: \nSelect and explain. \nA. Adenovirus, B. Parainfluenza virus, C. Rhinovirus, D. None of the above', 'role': 'user'}, {'content': 'Answer: B \nExplanation: 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.', 'role': 'assistant'}]