Most macromolecules are

• A. Non-covalent assemblies of small molecules
• B. Inorganic minerals
• C. Polymers made up of covalently linked chains of monomers
• D. Random aggregates of amino acids

Answer: (C)

Macromolecules are long polymers formed by covalently linking repeating monomer units. This covalent backbone—peptide bonds in proteins, phosphodiester bonds in nucleic acids, and glycosidic bonds in polysaccharides—gives them their high molecular weight and specific, stable structures. While many macromolecules can organize into complex shapes through noncovalent interactions, the defining feature is the covalently connected chain of monomers. Inorganic minerals and non-covalent assemblies of small molecules don’t have this covalent polymer backbone, and a random mix of amino acids wouldn’t form a true macromolecule without those covalent links.