This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cardiovascular system, Subject name: Physiology
At the end of the isometric relaxation phase 
Select and explain. 
A. Atrioventricular valves open, B. Atrioventricular valves close, C. Corresponds to "C" wave in JVP, D. Corresponds to T wave in ECG
A: Atrioventricular valves open
Answer: A: Atrioventricular valves open 
Explanation: At the end of Isovolumetric relaxation, the intraventricular pressures drop to less than the atrial pressure resulting in the opening of Atrioventricular valves Ref : Ganong 25th ed/page 539