Concept:Animal charcoal is a porous form of carbon that can adsorb colouring impurities from sugar solutions.Explanation:In sugar refining, the brown coloured solution is passed through animal charcoal or bone charcoal.The charcoal has a large surface area with many pores.Coloured impurities get adsorbed on this surface and are removed.This makes the sugar solution colourless and clean.Therefore, among the given options, charcoal is the allotrope of carbon used for this purpose.Answer:A. charcoal