Which type of water movement occurs from high concentration to low concentration?

• A. Osmosis
• B. Diffusion
• C. Bulk flow
• D. Capillary action

Answer: (B)

Diffusion captures the idea of substances moving from where they are more concentrated to where they are less concentrated, driven by random molecular motion. Water, like any dissolved substance, will diffuse down its concentration gradient in a solution. Osmosis is a specific case of diffusion that involves water moving across a semipermeable membrane, but since the prompt doesn’t mention a membrane, the general process described is diffusion. The other options aren’t about moving down a concentration gradient: bulk flow is pressure-driven bulk movement, and capillary action is driven by adhesion and cohesion in narrow spaces.