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
All are ECG changes in hypokalemia, except 
Select and explain. 
A. U wave, B. ST segment sagging, C. T-wave flattening or inversion, D. QT interval prolongation
D: QT interval prolongation
Answer: D: QT interval prolongation 
Explanation: None