Movement of solvent through semipermeable membrane.

• A. Diffusion
• B. Dialysis
• C. Filtration
• D. Osmosis

Answer: (D)

Osmosis is the movement of a solvent, typically water, across a selectively permeable (semipermeable) membrane toward the side with higher solute concentration. The membrane allows the solvent to pass while restricting many solutes, so water flows to dilute the more concentrated solution and raise the solvent’s chemical potential on the other side. This flow continues until the driving difference (osmotic pressure) is balanced by opposing forces such as hydrostatic pressure.

This is the specific process described by the question, whereas diffusion refers more generally to the movement of particles from high to low concentration without requiring a semipermeable barrier; filtration involves bulk flow through a membrane under pressure, and dialysis emphasizes solute movement across a membrane rather than solvent movement.