The answer is c. A and B are both correct
The solubility of some solid depends on temperature. Increased temperature of a solution will increase the kinetic energy of molecules in the solution. Solvent molecules will effectively break apart solute molecules. By breaking them apart, the surface area of solute molecules increases, too. Grinding the material will also break apart solvent molecules and increase their surface area. Increased surface area enables more solute molecules to interact with solvent molecules and the reaction rate increases.
Imagine if sugar will better dissolve in cold or hot water and also if icing sugar or granulated sugar will better dissolve.
Therefore, both increasing the temperature and grinding the material are important to increase the solubility of something.