Which of these statements regarding the conduction system of the heart is TRUE
A: The SA node is the heart’s natural pacemaker.
B: The SA node consists of a cluster of cells that are situated in the upper part of the wall of the right atrium (the right upper chamber of the heart).
C: When action potentials reach the AV node, they spread slowly through it.
D: Action potentials pass slowly through the atrioventricular node.