Which of the following best describes how a solution behaves when it reaches saturation?

When a solution reaches saturation, it means that the maximum amount of solute has been dissolved in the solvent at a specific temperature and pressure. In this state, any additional solute added to the solution will not dissolve unless the existing conditions change, such as increasing the temperature or pressure. This state reflects the dynamic equilibrium in a saturated solution, where the rate of dissolution of solute equals the rate of precipitation.

The other choices do not accurately describe this phenomenon. For instance, although the solute and solvent may be well mixed, they are not necessarily fully integrated in the sense that no additional solute can be dissolved. The description of the solute starting to decompose chemically does not apply in the context of saturation; saturation deals with the physical solubility of the solute rather than its chemical stability. Lastly, lowering the temperature is not a requirement for maintaining saturation; in fact, most solutes will dissolve better at higher temperatures, thus allowing more solute to enter the solution before saturation is reached.