A saturated solution contains the maximum amount of solute that can dissolve in a solvent at a given temperature. To make a saturated solution unsaturated, you can reduce the concentration of solute in the solution.
The most effective way to achieve this is:
A. by increasing the temperature of the solvent
Increasing the temperature typically increases the solubility of solids, allowing more solute to dissolve and thus making the solution unsaturated.
Therefore, the correct answer is A. by increasing the temperature of the solvent.