Diffusion wether be molecular or cellular implies the passage of a chemical species from a high concentration to low concentration, now in molecular diffusion there is no need to pass through a membrane, meanwhile, in cell diffusion, there is a passage through a semipermeable membrane. In this case, we have no cellular process listed or membranes involved, so we will stick to the molecular diffusion. Now with this definition, we can say that the correct answer is option A, because glucose molecules move from high concentration (sugar cristal) to low concentration (rest of the coffee).