People who have the o blood type possess 1) an enzyme that adds an n-acetylgalactosamine to the end of the oligosaccharide chain on rbc membrane glycolipids 2) an enzyme that adds a galactose to the end of the oligosaccharide chain on rbc membrane glycolipids 3) an enzyme that adds phospholipids to the end of the oligosaccharide chain on rbc membrane glycolipids 4) no enzymes capable of attaching galactose or n-acetylgalactosamine to the end of the oligosaccharide chain on rbc membrane glycolipids