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: Pediatrics
[{'content': 'Following is not a cause of stridor in infants \nSelect and explain. \nA. Croup, B. Laryngomalacia, C. Retropharyngeal abscers, D. Bronchiolitis', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]