Valve states during left ventricular systole

Steps:

• Recall that bicuspid (mitral) valve closes when ventricular pressure exceeds atrial pressure during systole.
• Note semi-lunar (aortic) valve opens when ventricular pressure surpasses aortic pressure.
• At time X, diagram shows rising ventricular pressure above both atrial and aortic levels.
• Thus, bicuspid closes to prevent backflow, while semi-lunar opens for ejection.

Why A is correct:

• During systole, high ventricular pressure closes bicuspid (preventing atrial reflux) and opens semi-lunar (allowing blood into aorta), per cardiac cycle physiology.

Why the others are wrong:

• B: Bicuspid open occurs in diastole, not when ventricular pressure rises.
• C: Both open only briefly at cycle start; not during pressure peak at X.
• D: Both closed happens in isovolumetric phases, not ejection at X.

Final answer: A