This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Electrolyte, Subject name: Medicine
A 12-year-old child with Renal tubular acidosis type 1 is having muscle cramps and weakness. ECG shows all except? 
Select and explain. 
A. T wave inversion with U waves, B. ST depression, C. Heart rate of 75 beats per minute, D. Absent P waves
D: Absent P waves
Answer: D: Absent P waves 
Explanation: Ans. (d) Absent P waves.In hypokalemia, the ECG shows1. Increased amplitude and width of the P wave2. Prolongation of the PR interval3. T wave flattening and inversion4. ST depression5. Prominent U waves (best seen in the precordial leads)6. Apparent long QT interval due to fusion of the T and U waves = long QU interval.