Which of the following descriptions best fits the term "osmosis"?

The term "osmosis" specifically refers to the movement of water molecules across a selectively permeable membrane in response to differences in solute concentrations, aiming to equalize the osmotic pressure on both sides of the membrane. This natural process occurs until equilibrium is reached, allowing for the maintenance of cellular environments. The focus is predominantly on the movement of water rather than solutes, emphasizing the equalizing effect that osmosis has on the concentrations of solutes, which is crucial for many biological functions and homeostasis.

In this context, while the other options address concepts related to movement across membranes and concentration gradients, they do not accurately define osmosis. The transfer of solute across a membrane pertains more broadly to diffusion rather than the specific process of osmosis. The passing of molecules without energy use could refer to passive transport but does not accurately capture the essence of osmosis as it specifically involves water. Lastly, movement against a concentration gradient describes active transport, which requires energy and is contrary to the passive nature of osmosis.