The correct answer is A. Isoprene.
Isoprene is a five-carbon hydrocarbon with the chemical formula $C_5H_8$. It is a colorless, flammable liquid that is found in natural rubber and turpentine. Isoprene is also used to make synthetic rubber, latex, and adhesives.
Vinyl chloride is a colorless, flammable gas with the chemical formula $C_2H_3Cl$. It is used to make polyvinyl chloride (PVC), a common plastic.
Acetylene is a colorless, flammable gas with the chemical formula $C_2H_2$. It is used to make plastics, synthetic fibers, and other chemicals.
Neoprene is a synthetic rubber that is made from chloroprene. It is a tough, durable material that is resistant to heat, oil, and chemicals. Neoprene is used to make a variety of products, including gaskets, hoses, and roofing materials.