Osmosis is the movement of water from an area of high concentration to an area of low concentration through a semipermeable membrane. Which process is this?

• A. Osmosis
• B. Diffusion
• C. Active Transport
• D. Filtration

Answer: (A)

Osmosis is water moving through a selectively permeable membrane from where water is more available (lower solute concentration) to where water is less available (higher solute concentration). The defining feature is that the membrane allows water to pass but restricts most solutes, so the movement is driven by differences in solute concentration, not by energy input. In the described scenario, water crosses the membrane in this way, so the process is osmosis.

Diffusion involves solute particles spreading out down their own concentration gradient, which may not involve a membrane or water specifically. Active transport requires energy to move substances against their gradient. Filtration relies on pressure to push water and solutes through a filter, not on selective membrane movement of water alone.