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': 'Sine wave pattern in E.C.G. is seen in- \nSelect and explain. \nA. Hypokalemia, B. Hyperkalemia, C. Hyponatremia, D. Hypermatremia', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]