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': 'Tracheal bifurcation is at which level of vertebra \nSelect and explain. \nA. T4, B. T2, C. T1, D. T7', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Trachea divides at the level of lower border of 4th thoracic vertebrae into 2 primary principal bronchus.', 'role': 'assistant'}]