Which of the following scenarios describes osmosis?

The correct answer describes osmosis as the flow of water from a region of high concentration to a region of low concentration. Osmosis specifically refers to the movement of water molecules through a semipermeable membrane. This movement occurs in response to the concentration gradients of solutes—water moves to balance solute concentrations on either side of the membrane, facilitating equilibrium.

In biological systems, this mechanism is crucial for maintaining cell turgor, regulating hydration levels, and ensuring that essential biochemical processes can occur within cells. Water's ability to move in this way helps cells manage their internal environments effectively, demonstrating the principle that water will naturally flow toward areas where there is a lower concentration of water (and, consequently, a higher concentration of solutes).

The other scenarios provided refer to different biological processes. The movement of glucose into a cell typically involves active transport or facilitated diffusion rather than osmosis, as glucose is a solute that cannot cross cell membranes without assistance. The transport of sodium ions out of the cell involves active transport as well, specifically through mechanisms like the sodium-potassium pump. Absorption of nutrients in the intestines involves various transport mechanisms including active transport and diffusion, but does not specifically illustrate osmosis as it pertains to water movement.