The correct option is B Polymer formed is known as polyisoprene
CH≡CHCu2Cl2/NH4Cl−−−−−−−−−→ΔCH2=CH−C≡CH(A)HCl−−→H2C=CH−C|Cl=CH2(B)
Acetylene dimerises to give vinyl acetylene, which is then combined with HCl to afford 4-chloro-1,2-butadiene (B), which in the presence of copper(I) chloride, rearranges to the targeted 2-chlorobuta-1,3-diene.
Polymerisation of B (chloroprene) yields neoprene, a synthetic rubber which is formed by 1,4-addition.