Isovolumetric contraction phase Steps:

• AV valve closes once RV pressure exceeds RA pressure, establishing RA < RV.
• Semilunar valve stays closed while RV pressure remains below PA pressure, so RV < PA and RA < PA.
• Both valves closed as RV pressure builds without volume change.
• This matches the pressure condition in isovolumetric contraction.

Why C is correct:

• Isovolumetric contraction is defined as the period of closed AV and semilunar valves with rising ventricular pressure between atrial and arterial levels.

Why the others are wrong:

• A: Semilunar valve open during ejection, when RV > PA.
• B: AV valve open equalizes RA and RV pressures, violating RA < RV.
• D: Both valves open simultaneously does not occur; AV open also equalizes RA and RV.

Final answer: C