This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cardio thoracic surgery  , Subject name: Surgery
[{'content': 'Most common tumor in the posterior mediastinum is \nSelect and explain. \nA. Neurofibroma, B. Teratoma, C. Lymphoma, D. Bronchogenic cyst', 'role': 'user'}, {'content': "Answer: A \nExplanation: Most common tumour of posterior mediastinum is neurofibromas constituting 75% of the total.Others include ganglioneuromas,aneurysm of descending aoa,lymph node mass. Reference: SRB's manual of surgery,5th edition,page no:1126.", 'role': 'assistant'}]