An unsaturated solution can be converted to saturated solution
A. by adding more solute to the solvent
B. by removing solute from the solvent
C. by increasing temperature
D. both b and c

Hint: Saturated solution is a solution having maximum soluble concentration of the solute and an unsaturated solution has a concentration less than the concentration of solute in a saturated solution. We need to increase concentration of solute in solution to attain a saturated solution.
Complete step-by-step answer:

An unsaturated solution is a chemical solution in which the solute concentration is lower than its equilibrium or maximum solubility. All of the solute added to the solvent dissolves in it completely. When a solute (often a solid) is added to a solvent (often a liquid), both the processes occur simultaneously.
A saturated solution is a chemical solution containing the maximum concentration of a solute dissolved in the solvent. Solubility increases with temperature and saturated solution gets converted to unsaturated solution. The increase in kinetic energy that comes with higher temperatures allows the solvent molecules to more effectively break apart the solute molecules that are held together by intermolecular attractions.
Thus, if we add more solute the unsaturated solution can be converted to saturated solution. Hence, the correct option is option A.

Note: We can experimentally determine if the given solution is saturated or unsaturated If we add more solute and it does not dissolve, then the original solution was saturated. If the more added solute dissolves, then the original solution was unsaturated.