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.
It’s C because at higher temperatures particles move faster
Answer:
The answer should be C.
An energy pyyramid shows how the energy "flows" from organism to organism as it goes up.
Explanation:
The valence electrons determine the group the elements belong in the periodic table. For example, the element sodium, Na, has a valence electron of one and so it belongs to Group 1 in the periodic table. Another example is Aluminium, Al, which has a valence electron of three and therefore it belongs to Group 3 in the periodic table.
