Which phenomenon describes the movement of solvent through a semipermeable membrane?

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

Answer: (D)

Osmosis is water moving through a semipermeable membrane toward higher solute concentration to balance chemical potential. The membrane lets water pass but blocks most solutes, so the solvent flow continues until the driving forces balance (or hydrostatic pressure offset reaches equilibrium). This differs from diffusion, which generally describes the random movement of solute particles down their concentration gradient; filtration, which is driven by hydrostatic pressure pushing solvent and solutes through a porous barrier; and dialysis, which relies on diffusion across a membrane to separate solutes, not just the selective movement of solvent.