What is polymerization?

a. Polymers that soften when exposed to heat but then return to their original shape when cooled
b. Polymers that solidify or set irreversibly when they are heated
c. The chemical reaction in which monomer molecules are linked and cross-linked into macromolecules
d. Synthesis of a polymer that is characterized by the ability of its molecules to elongate when strained and to reversibly assume their original shape when the tension has been released

C