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: Microbiology
[{'content': 'Most common Cause of Acute Laryngotraheobronchitis is: \nSelect and explain. \nA. Parainfluenza virus, B. H. influenza, C. Influenza virus, D. Measles', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Parainfluenza virus', 'role': 'assistant'}]