What indicates that a solution is saturated?

A solution is considered saturated when it contains the maximum amount of solute that can be dissolved in a solvent at a specific temperature and pressure. In this state, any additional solute added to the solution will not dissolve and will remain as an undissolved solid. The presence of undissolved solid is a clear indication that the solution has reached its saturation point; the solute in excess indicates that the solvent cannot accommodate any more solute particles into solution.

The other options do not provide clear evidence of a saturated solution. Lack of odor is not relevant to the saturation of a solution, as many substances may have little to no odor regardless of their concentration. An increase in temperature typically increases the solubility of many solutes, which would allow more solute to dissolve rather than indicating saturation. Lastly, the formation of bubbles can indicate gas release or other phenomena but does not necessarily relate to the saturation of a solution. Thus, the presence of undissolved solid is the correct indicator of a saturated solution.