A means of water erosion would not be C. natural water springs. Erosion occurs when water or wind removes rock, dissolved material, and soil from one location to another. All the other options describe water moving from one location to another, which accurately describes what erosion does.
Osmosis only talks about water molecules
Diffusion talks everything other then the water molecules.
So,
Osmosis : water molecules travel from a region of a higher water potential to a region of lower water potential through a partially permeable membrane via osmosis
Diffusion : Travels from a region of higher concentration to a region of lower concentration through a partially permeable membrane via diffusion
