Answer:
The correct answer is diffusion.
Diffusion is type of passive transport in which a substance is transported down the concentration gradient across the semi-permeable membrane.
In other words, a particle or molecule moves from the region of high concentration to the region of low concentration.
The particles or molecules keep moving until their concentrations become equal or uniform across the membrane.
In contrast, osmosis refers to the movement of water or solvent from the region of less concentration (of solute) to the region of high concentration (of solute) across the semi-permeable membrane.