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: Anatomy
[{'content': 'Pierre Robin sequence is caused by defect in development of which pharyngeal arch? \nSelect and explain. \nA. I, B. II, C. IV, D. None of the above', 'role': 'user'}, {'content': "Answer: A \nExplanation: Robin sequence may occur independently or in association with other syndromes and malformations. Like Treacher Collins syndrome, Robin sequence alters first-arch structures, with development of the mandible most severely affected. Infants usually have a triad of micrognathia, cleft palate, and glossoptosis (posteriorly placed tongue) Ref: Langman's embryology 11th edition Chapter 16.", 'role': 'assistant'}]