Concept:This phenomenon is an example of diffusion, the natural spreading of particles from a region of higher concentration to a region of lower concentration.
Explanation:Although the cup of water is left undisturbed, the salt grains dissolve gradually at the bottom.
This creates a region of high salt concentration near the grains and a region of low salt concentration elsewhere in the water.
Because of random thermal motion, the dissolved salt particles move continuously from the concentrated region to the less concentrated regions.
Over time, these particles spread evenly throughout the water, making all of it taste salty.
This movement does not require stirring or any external force.
Hence, the process is not convection, osmosis, or capillarity, but simply diffusion.
Answer:D. diffusion