Since the other answer got deleted, i'll just answer it for you.
a sinoatrial node is the main pacemaker that begins each heartbeat located in the junctions of superior vena cava and the right atrium. It signals from the node that spread through the atria and determines the heart rates.
Answer:
Solar flare
Explanation:
They are characterized by coronal mass ejections on the sun's surface. The ejected ionized particles if thrown in the direction of the earth will cause bright aurora as they colide with the earth’s ionosphere and magnetic field. These solar storms can also affect telecommunications satellites and also electricity grid systems.
Answer:
I think D) Glycolysis
Explanation:
<em>Glycolysis</em> is the <em><u>first pathway</u></em> used in the breakdown of glucose to extract energy. It takes place in the cytoplasm of both prokaryotic and eukaryotic cells. It was probably one of the earliest metabolic pathways to evolve since it is used by nearly all of the organisms on earth.
