Concept:Decolourization by charcoal is a surface phenomenon called adsorption.Explanation:Charcoal has a highly porous structure with a large surface area.This allows it to attract and hold coloured impurities on its surface.The process of attracting molecules to a surface is called adsorption, not absorption.Therefore, charcoal adsorbs the colouring matter from sugar solution.Answer:D. adsorption property.