This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory system, Subject name: Anatomy
[{'content': 'Most common cause of mediastinitis is : \nSelect and explain. \nA. Tracheal rupture, B. Esophageal rupture, C. Drugs, D. Idiopathic', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Most cases of acute mediastinitis either are due to esophageal perforation or occur after median sternotomy for cardiac surgery. Ref Harrison 19th edition pg 1719', 'role': 'assistant'}]