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': 'Which of the following aoic arches regress during development: \nSelect and explain. \nA. II, B. IV, C. V, D. VI', 'role': 'user'}, {'content': "Answer: C \nExplanation: The aoic sac contributes a branch to each new arch as it forms, giving rise to a total of five pairs of aeries. (The fifth arch either never forms or forms incompletely and then regresses. Consequently, the five arches are numbered I, II, III, IV, and VI Ref: Langman's embryology 11th edition Chapter 12.", 'role': 'assistant'}]