This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Heart, Circulation, and Blood, Subject name: Physiology
At the end of isometric relaxation phase 
Select and explain. 
A. Atrioventricular valves open, B. Atrioventricular valves close, C. Corresponds to peak of "C" wave in JVP, D. Corresponds to T wave in ECG
A: Atrioventricular valves open
Answer: A: Atrioventricular valves open 
Explanation: Ans. (a) Atrioventricular valves openRef: Ganong, 25th ed/p.539Isovolumetric relaxation ends by opening of Atrioventricular valves