15. POLYMERS (HM)
Explanation:
Molecular mass is a number equal to the sum of the atomic masses of the atoms in a molecule.
A monomer is a molecule that forms the basic unit for polymers.
A dimer is an oligomer consisting of two monomers joined by bonds that can be either strong or weak, covalent, or intermolecular.
A polymer is a chemical compound with molecules bonded together in long, repeating chains.
An oligomer is a molecular complex of chemicals that consists of a few repeating units.
The polymer has the highest number of repeating units and hence, the maximum number of atoms, so it has the largest molecular mass.