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: Physiology
True about fourth heart sound is 
Select and explain. 
A. Occurs at end of P wave in ECG, B. Occurs at end of T wave in ECG, C. Occurs during early rapid filling phase of ventricular diastole, D. Occurs during slow ejection phase of Ventricular systole
A: Occurs at end of P wave in ECG
Answer: A: Occurs at end of P wave in ECG 
Explanation: None