Which of the following would be the best practice to determine the right amount of charcoal to use in recrystallization of an impure sample? a. Visualize the color of the content in the recrystallization flask after the addition of charcoal. b. Visualize the color of the filtrate from the hot filtration. c. Transfer an estimated amount of charcoal with a spatula. d. Measure out the exact quantity of charcoal with a balance.