Blood group antigens belong to the class

For red blood cells, the membrane oligosaccharides that determine the antigenic natures of the ABO substances appear to be mostly present in glycosphingolipids, whereas in secretions the same oligosaccharides are present in glycoproteins. Some examples of conjugated proteins are lipoproteins, glycoproteins, phosphoproteins, hemoproteins, flavoproteins, metalloproteins, phytochromes, cytochromes, opsins and chromoproteins. so the ABO substances can be chosen as Conjugated proteins from the given options Ref: Harper's Illustrated Biochemistry, 30E (2015) Pg No. 697 chapter 53.