Final answer:
Option A) The intracellular fluid (ICF), which lies within cells, contains the most water in the human body, accounting for about 60 percent of the total water content.
Step-by-step explanation:
The intracellular fluid (ICF) compartment contains the most water in the human body. The ICF is the fluid within cells, making up about 60 percent of the body's total water content. In an average-sized adult male, this translates to roughly 25 liters of fluid. The ICF is a vital component of the cells' cytosol/cytoplasm, and its volume is highly regulated to ensure proper cellular function. If water content is too low, cellular activities could be hampered due to high solute concentration, and if water content is too high, cells may burst.
By contrast, the extracellular fluid (ECF), which includes both plasma and interstitial fluid (IF), accounts for the remaining one-third of the body's water. Plasma, the fluid component of blood, represents approximately 20 percent of the ECF, and is essential for transporting materials such as blood cells, nutrients, and waste products throughout the body. The IF surrounds all non-blood cells and acts as a medium for the exchange of substances between cells and plasma.