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: Unknown
[{'content': 'Dysphagia lusoria is most commonly caused by- \nSelect and explain. \nA. Aberrant Hemiazygous vein, B. Aberrant right subclavian artery, C. Enlarged mediastinal nodes, D. Thymoma in mediastinum', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is 'b' i.e., Aberrant right subclavian artery o Has been explained in previous sessions.", 'role': 'assistant'}]