Which one of the following polymers is NOT obtained by condensation...

Buna-N is an addition polymer formed by the copolymerisation of $1,3$-butadiene and acrylonitrile.

Nylon $6,6$ is a condensation polymer of hexamethylenediamine and adipic acid.

Bakelite is a condensation polymer of phenol and formaldehyde.

Terylene is a condensation polymer of ethylene glycol and terephthalic acid.

Answer: Buna-N