Answer:
SA node
Explanation:
The SA node (called the pacemaker of the heart) sends out an electrical impulse. The upper heart chambers (atria) contract. The AV node sends an impulse into the ventricles. The lower heart chambers (ventricles) contract or pump.
Serpentine minerals are made of tiny sheets of silica tetrahedrons that are loosely held together.
A
my was the same but A,B,C,D
It tends to resist rising.
