This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General anatomy, Subject name: Anatomy
[{'content': 'Arch of aoa is derived from all except \nSelect and explain. \nA. Left horn of aoic sac, B. Left 2nd arch aery, C. Left 4tharch aery, D. Left dorsal aoa', 'role': 'user'}, {'content': "Answer: B \nExplanation: Arch of aoa develops from aoic sac, left horn of aoic sac and left 4th arch aery. Ref: Gray's 39e/p-210-220", 'role': 'assistant'}]