Biofuel, which is chemical energy taken from biodegraded material.
The valves in the heart make sure that blood goes in only one direction. For example, when blood is pumped from the left ventricle the mitral valve won't allow the blood to come back into the left atrium. And the aortic valve will prevent the blood from coming back into the left atrium from the aortic arch.
It would be b hope you get it right
