`SBR(GRS,Buna-S,Cold Rubber)is obtained by free radical intiator.The most commenly used free radical initiator is:
A. Buta`-1,3-` dinene `(70%)` and `30%` phenyl ethene (styrene)
B. Chloroprene and styrene
C. Vinyl acetylene and styrene
D. Isoprene and `1,3-` butadiene