Rehydration replaces which fluid compartment?

• A. Intracellular fluid
• B. Extracellular fluid
• C. Plasma
• D. Interstitial fluid

Answer: (A)

The key idea is that rehydration aims to restore the water inside cells, so intracellular fluid is the focus. When dehydration occurs, cells lose water and their volume shrinks, which impairs cellular functions. Providing fluids reestablishes the osmotic balance and allows water to move back into cells, expanding the intracellular compartment and helping cells function again. The extracellular spaces (plasma and interstitial fluid) are also replenished, but the immediate, defining effect of rehydration on restoring cellular function comes from rehydrating the intracellular fluid.