Solution

Chain growth (addition) polymers are formed by repeated addition of monomer molecules having a double bond, through free radical, cationic or anionic chain reactions, without loss of any small molecule.
Polystyrene is made by free radical polymerisation of styrene: $n\,C_6H_5CH=CH_2 \rightarrow [-CH(C_6H_5)-CH_2-]_n$. It is a chain growth polymer.
Nucleic acids, proteins and starch are natural condensation (step growth) polymers. They are formed by joining monomers (nucleotides, amino acids and glucose) with loss of water molecules, through phosphodiester, peptide and glycosidic linkages.
So the chain growth polymer is polystyrene.

Concept Chain growth versus step growth polymers

Polymers in past papers

34 questions from this chapter have appeared across 23 exam years.