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': 'All are ECG changes in hypokalemia, except \nSelect and explain. \nA. U wave, B. ST segment sagging, C. T-wave flattening or inversion, D. QT interval prolongation', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]