Ventricular Systole: Ventricles Contract to Eject Blood

Steps:

• Recall ventricular systole as the phase when ventricles contract, increasing pressure to eject blood.
• Identify key events: AV valves close to prevent backflow; semilunar valves open for outflow to arteries.
• Atria remain relaxed (diastole), so no atrial contraction or AV valve opening occurs.
• Match to options: only the event tied to semilunar valve opening (likely 3) is correct.

Why D is correct:

• Ventricular systole specifically involves semilunar valves opening as ventricular pressure exceeds arterial pressure, allowing blood ejection (per cardiac cycle physiology).

Why the others are wrong:

• A and B include 1 and/or 2, which likely refer to atrial contraction or AV valve opening, occurring in atrial systole, not ventricular.
• C selects 2 only, which probably describes AV valve function irrelevant to ventricular contraction phase.

Not enough information on exact statements 1–3 for full precision.

Final answer: D