Which statement correctly describes osmotic movement in body fluids?

• A. Movement of water across a semipermeable membrane toward higher solute concentration
• B. Movement of solute particles from high to low concentration
• C. Active transport of water across membrane
• D. Filtration by hydrostatic pressure

Answer: (A)

Osmosis is the movement of water across a semipermeable membrane toward the side with higher solute concentration. In the body, membranes like cell and capillary walls let water pass but restrict many solutes, so water shifts to the compartment with more dissolved particles to balance solute levels. This passive flow explains why cells shrink in a hypertonic solution and swell in a hypotonic one.

The other descriptions don’t fit osmosis: moving solute particles from high to low concentration is diffusion of solutes, not water movement; active transport of water would require energy and isn’t how water passage is driven; and filtration involves water movement driven by hydrostatic pressure, not by solute concentration differences.