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': 'The thoracic duct crosses the posterior mediastinum at the level of which vertebra- \nSelect and explain. \nA. T5, B. T6, C. T7, D. T8', 'role': 'user'}, {'content': 'Answer: A \nExplanation: At the level of T5, thoracic duct crosses from right to left.', 'role': 'assistant'}]