This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.N.S, Subject name: Medicine
[{'content': 'Thymoma associated with \nSelect and explain. \nA. Myasthenia gravis, B. Polycythemia, C. Ectopic ACTH, D. Polyaentis nodosa', 'role': 'user'}, {'content': 'Answer: A \nExplanation: * Thymus is abnormal in 75% patients with MG. 65% - hyperplastic, 10%- thymic tumours or thymomas Ref Harrison20th edition pg 2345', 'role': 'assistant'}]