The answer is D. Phospholipids are diglycerides (two fatty acid chains covalently bonded to a glycerol molecule) that are covalently bonded to a phosphate group by an ester linkage. Fatty acids are long chains that are mostly made up of hydrogen and carbon, while phosphate groups consist of a phosphorus molecule with four oxygen molecules attached. Glycerol is a 3 carbon chain containing hydroxyl groups in each of the carbon.