Final answer:
Plasma, interstitial fluid, and intracellular fluid have the same osmotic pressure but different ion composition.
Step-by-step explanation:
The answer to the question is c. have the same osmotic pressure but different ion composition. Plasma, interstitial fluid, and intracellular fluid have the same osmotic pressure, but their ion composition differs. Osmotic pressure is regulated by the movement of water across membranes, and the volume of the fluid compartments can change temporarily. The specific concentrations of important electrolytes in these fluid compartments are closely regulated by mammalian systems.