While performing a recrystallization, a chemist notices that a small amount of the sample will not dissolve, even after the recrystallization solution has been boiling for some time. Select the correct course of action.
A. Perform a gravity filtration with a stemless funnel.
B. Perform a gravity filtration with a long-stemmed funnel.
C. Isolate the insoluble material via filtration, grind it into a powder, and add it back to the recrystallization solution
D. Cool the recrystallization solution to room temperature and then heat it again to dissolve the insoluble material.