The correct choice is (d) Glycosaminoglycan
For explanation: A more complex structures of polysaccharides is glycosaminoglycan (GAGs). Unlike other polysaccharides, they have an A-B-A-B where A and B represent two different sugars. An example of GAG is heparin, which is secreted by cells in lungs against tissue damage. Heparin prevents blood coagulation, enabling free flow of blood to heart or lungs.