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Osmosis is a special case of diffusion involving water moving through a semipermeable membrane toward the region with higher solute concentration (i.e., lower water potential). Option C captures all essential features: water, semipermeable membrane, and direction relative to solute concentration. Option A is generic diffusion (not specific to water or membranes). Option B describes active transport, which requires energy (ATP) to move substances against concentration gradients. Option D describes bulk flow (e.g., blood pressure in vessels), which is driven by pressure, not primarily by solute concentration differences across a selective membrane. On GED Science, pay attention to the substance (water vs. solute), the barrier (semipermeable), and whether energy is required (osmosis is passive). Visualizing a U-tube with a membrane and different solute concentrations can help: water rises on the high-solute side because it crosses to equalize water potential.