Which of the following polymers has molecular mass an integral multiple of molecular mass of its monomer?

Buna rubber is addition polymer molecular mass is integral multiples of molecular weight of its monomers.

Buna-S is a synthetic polymer made up from the combination of butadiene and styrene. It is a copolymer of 75%$75\mathrm{\%}$ butadiene and 25%$25\mathrm{\%}$ styrene.

Buna-S is a synthetic polymer made up from the combination of two monomer units. It is formed in the polymerization process at low temperature that’s why it is also called cold rubber. This rubber is also termed as styrene butadiene rubber (SBR).