ANS:D - None of these

The correct answer is: None of these. All the options listed (polyisoprene, neoprene, and nitrile-butadiene) are elastomers. Here’s a brief overview of each:

1. Polyisoprene: This is the synthetic version of natural rubber and is known for its excellent resilience, tensile strength, and elasticity.
2. Neoprene: This is a synthetic rubber also known as polychloroprene. It is resistant to oil, chemicals, and weathering, making it suitable for a variety of applications, including wetsuits and gaskets.
3. Nitrile-butadiene: Commonly known as NBR or nitrile rubber, it is resistant to oils and fuels, making it ideal for use in the automotive and aeronautical industries.