Which statement correctly describes diffusion?

• A. It requires bulk movement of water.
• B. It is movement of substances from high to low concentration.
• C. It moves water from low to high concentration.
• D. It only occurs in living organisms.

Answer: (B)

Diffusion is the passive spread of particles from areas of higher concentration to areas of lower concentration, driven by the random motion of molecules. It happens without energy input and without the need for bulk movement of water. In soils, this means solutes such as nutrients or salts can move from where they’re more concentrated into surrounding soil just because of the concentration gradient, even when there isn’t a bulk water flow. The statement that diffusion moves water from low to high concentration would go against the gradient, which is not how diffusion works. And diffusion isn’t limited to living systems; it occurs in air, water, and solids alike, independent of living organisms.