Which of the following is a synthetic rubber?

All of these

The correct answer is option 4. All of these.

Buna-S: It is copolymer of 1, 3-butadiene and styrene. It is obtained by the polymerization of butadiene and styrene in the ratio of 3:1 in the presence of sodium.

Buna-N: It is obtained by the co-polymerization of 1, 3-butadiene and acrylonitrile in the presence of a peroxide catalyst.

Neoprene: Neoprene or polychloroprene is formed by the free radical polymerisation of chloroprene.