ANS:C - super-saturation

The driving potential for crystal growth during crystallization is the super-saturation of the solution. Super-saturation refers to a state where the concentration of a solute in a solution exceeds its equilibrium solubility at a given temperature and pressure. In other words, the solution contains more dissolved solute than it would under equilibrium conditions. This excess of solute molecules provides the driving force for crystal nucleation and growth. When a solution is super-saturated, the solute molecules are more likely to come together and form nuclei, which can then grow into larger crystals. The higher the degree of super-saturation, the faster and more extensively crystal growth can occur. So, the correct answer is: super-saturation.