Maybe water Ian nothing B because it’s not C
The molecules in the sugar move from an area of higher concentration (sugar cube) to an area of lower concentration in the water.
That is exactly what diffusion is: the net movement of molecules or atoms driven by a gradient , which means that it doesn’t requires energy.
Water typically diffuses in and out of cells depending on the concentration of solutes (other gunk not water) in both the cell and the external environment. Osmosis (the diffusion of water), happens from where the solute concentration is lowest to where the solute concentration is highest (or more sensibly, water travels to dilute the solute; so imagine if a cell with a lot of gunk in it swims into pure water, water will start to move into the cell).
Answer:
They help transport glucose into the brain, clean the brain of excess chemicals and may even affect the intensity of the neurons' communications