It would have to be the variable
1) Pulmonary Circulation:This is the process where
deoxygenated blood is carried away from
the right ventricle of the hearth while oxygenated blood is returned to the
left ventricle and atrium of the heart.
2) Heart: It is a muscular organ that pump blood through the blood
vessels of the circulatory system.
3) Systemic vain: <span>this is a vain that drain into the right right
atrium </span>
4) Physical exertion:It the expenditure of energy expended during physical
activity.
5) Vasoconstriction:It can be defined as the narrowing of the blood vessels which
result into contraction of the muscular wall of the vessels most especially
large arteries and small arterioles.
6) Vasodilation: This is when blood vessel is widening and result in
relaxation of smooth muscle cell within the vessel walls.
Based on the letters in the diagram
A= cell
B= nucleus
C= chromosomes
D= gene
E= DNA
F= protein
the world would start to rebuild its self