Which type of solution is characterized by having dissolved all possible solute?

A saturated solution is defined as one in which the maximum amount of solute has been dissolved in a solvent at a given temperature and pressure. When a solution reaches this state, any additional solute added will not dissolve and will remain as a separate phase, typically settling at the bottom or floating if it is less dense than the solvent.

In a saturated solution, the solute molecules are in equilibrium with the solid phase of the solute. This means that the rate at which the solute dissolves is equal to the rate at which the solute precipitates out of the solution. Therefore, a saturated solution is characterized by having dissolved all possible solute it can hold under the specific conditions.

This stands in contrast to a sub-saturated solution, which has not yet reached this maximum capacity and can still dissolve more solute. A supersaturated solution, on the other hand, contains more solute than would normally dissolve at a given temperature, achieved by manipulating temperature or other conditions, making it unstable. A mixed solution generally refers to a combination of different components but does not specify the saturation status.

Thus, the correct identification of the saturated solution illustrates the definitive nature of solute-solvent interactions at equilibrium.