The correct option is C can add more solute
An unsaturated solution can add more solute into it. The term saturated solution is used in chemistry to define a solution in which no more solute can be dissolved in the solvent. It is understood that saturation of the solution has been achieved when any additional substance that is added results in a solid precipitate or is let off as a gas. In the state where solution is still not saturated, more solute can be added until the state of saturation is reached.