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: Medicine
[{'content': 'Most common tumor of the anterior mediastinum tumour is - \nSelect and explain. \nA. Thymoma, B. Lymphoma, C. Neurogenic tumour, D. Vascular cyst', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]