What causes the atrioventricular valves to close during a heartbeat? a Pressure in the atria is higher than in the ventricles. b Pressure in the atria is lower than in the ventricles. c Pressure in the arteries is higher than in the ventricles. d Pressure in the arteries is lower than in the ventricles.

The correct answer is -  b Pressure in the atria is lower than in the ventricles.

Explanation:

The atrioventricular valves close when the pressure in the ventricles is more than the pressure in the atria. Which leads to the contraction of the papillary muscles to shut the leaflets of the valves,

When the ventricles relax, atrial pressure exceeds ventricular pressure, the AV valves are pushed open and blood flows into the ventricles. However, when the ventricles contract, ventricular pressure exceeds atrial pressure causing the AV valves to snap shut.

what's the question?

d. planting trees

the trees take in carbon to make oxygen.