The answer should be D, water; reach equilibrium.
Osmosis is only the movement of water, down the water potential gradient. Movement of other substances should be involved in diffusion or active transport instead.
The goal of osmosis (also diffusion) is to make the concentration of substance (water potential for osmosis) the same. This is the meaning of equilibrium. Water molecules won't stop moving after equilibrium is reached, but there no net flow, meaning the amount of water molecules flowing from the left to right for example is same as the molecules flowing from right to left. So, the second answer is to reach equilibrium.
The answer is D.