Why is there a delay in the action potential in the AV node?
a. It allows time for the atria to be filled with blood.
b. It allows the action potential to reach both ventricles at the same time.
c. It allows an action potential to reach the left atrium so both atria contract together.
d. It allows an action potential to reach the left atrium so both atria contract together, before the ventricles contract.