Answer:
C. sugar crystals with stirring at 15oC
Step-by-step explanation:
Solubility is the amount of solute that will dissolve in a solvent to form a solution. Solubility increases with increase in temperature. The increase in temperature increases the average kinetic energy of the solute and solvent molecules causing them to collide frequently. Also the increase in surface area of the solute increases effective collision between solute and solvent particles.