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': 'Thymoma is associated with: \nSelect and explain. \nA. Myasthenia gravis, B. Hypergammaglobulinemia, C. SLE, D. Multiple sclerosis', 'role': 'user'}, {'content': "Answer: A \nExplanation: Approximately 75% of the patients with myasthenia gravis may have thymic abnormalities. About 30% of the patients with myasthenia gravis have thymoma. So Myasthenia gravis is the single best answer of choice. Ref: Harrison's Principles of Internal Medicine, 16th Edition, Page 2521", 'role': 'assistant'}]