During the cardiac cycle, which phase begins immediately after the closure of the aortic valve and ends with the opening of the mitral valve?

✓ Correct Answer: Option C

After aortic valve closure, the ventricles relax, but the mitral valve is also closed, so no blood enters or leaves, causing isovolumetric relaxation. This period ends when ventricular pressure falls below atrial pressure, opening the mitral valve.