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': "Atrial fibrillation is common in: \nSelect and explain. \nA. Adrenogenital syndrome, B. Addison's disease, C. Hyperthyroidism, D. Von-Willebrand's disease", 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]