b. Exchange between the plasma and the intracellular fluid occurs across the cell membrane.
Explanation:
The body fluid can be categorized as extracellular and intracellular fluid. The fluid within cells is called intracellular fluid and the body fluid outside body cells makes the extracellular fluid. The interstitial fluid is the extracellular fluid that is present in the narrow spaces between cells of tissues.
On the other hand, the extracellular fluid present within blood vessels is termed blood plasma. Therefore, plasma and intracellular fluid can exchange material via interstitial fluid only, not directly via the cell membrane. The exchange between interstitial fluid and intracellular fluid occurs across the cell membrane.
