The blood in the left side of the heart is oxygenated/deoxygenated. why is this logical?

Because blood is pumped to the lungs, where we can find fresh blood. The blood in the RIGHT side of the heart is deoxygenated. The left side of the heart is the one which receives oxygenated blood. It comes directly from the pulmonary vein. It is further pumped into the aorta. The right side of the heart receives deoxygenated blood from the phenomenon called vena cava. Then, it’s pumped into the pulmonary vein.

fluid balance is an aspect of the homeostasis of organisms in which the amount of water in the organism needs to be controlled, via osmoregulation and behavior, such that the concentrations of electrolytes (salts in solution) in the various body fluids are kept within healthy ranges. the core principle of fluid balance is that the amount of water lost from the body must equal the amount of water taken in.