Proteoglycans are part of the extracellular matrix; they provide structure, viscosity and lubrication, and adhesiveness. They are composed of proteins conjugated to carbohydrate components called glycosaminoglycans. The glycosaminoglycan component makes up the majority of the mass of a proteoglycan. Which of the following are possible components of glycosaminoglycans? Select all that apply. a. beta-D-fructofuranose b. amylose c. uronic acid d. N- acetylglucosamine