This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Oesophagus, Subject name: Surgery
[{'content': "Hamman's sign is seen with: \nSelect and explain. \nA. Acute pericarditis, B. Aortic dissection, C. Tracheal compression, D. Esophageal perforation", 'role': 'user'}, {'content': "Answer: D \nExplanation: Ans. d (Esophageal perforation). (Ref. Harrison's medicine 16th ed. 1569)Hamman's sign (Laennec-Hamman symptom, Laennec-Miiller-von Bergmann, Hamman's crunch)# A crunching, rasping sound, synchronous with heartbeat, heard over the precordium and sometimes at a distance from the chest in spontaneous mediastinal emphysema.# Hamman's sign may be present in acute mediastinitis, for e.g. as in esophageal perforation. It is a crunching sound that is heard over the anterior chest in synchrony with cardiac systole.", 'role': 'assistant'}]