Which electrolyte is the primary regulator of fluid volume?

A) Potassium
B) Calcium
C) Sodium
D) Magnesium

Sodium is the major action in the extracellular fluid (ECF).Its primary function is to regulate fluid volume.When sodium is reabsorbed in the kidney,water and potassium are also reabsorbed,thereby maintaining ECF volume.Potassium is a key electrolyte in cellular metabolism.Calcium is responsible for bone health and neuromuscular and cardiac functions.It is also an essential factor in blood clotting.Magnesium is a mineral used in more than 300 biochemical reactions in the body.