The correct answer is option 3. PHBV.
Let us discuss each of the mentioned polymers in more detail:
(1) Novolac:
Novolac is a type of phenolic resin. Phenolic resins are synthetic polymers made by the reaction of phenol (an aromatic alcohol) with formaldehyde. Novolacs are usually thermosetting polymers, meaning they undergo irreversible chemical reactions upon curing. While these resins can have useful properties, they are generally not considered biodegradable.
(2) Neoprene:
Neoprene is a synthetic rubber, also known as polychloroprene. It is produced by the polymerization of chloroprene. Neoprene is widely used in various applications, including wetsuits, gaskets, and industrial hoses. However, it is not biodegradable and can persist in the environment for a long time.
(3) PHBV (Polyhydroxybutyrate-co-hydroxyvalerate):
PHBV is a biodegradable synthetic polymer belonging to the family of polyhydroxyalkanoates (PHAs). PHBV is produced by certain bacteria as intracellular granules. It is considered biodegradable under natural conditions. Unlike traditional plastics, which may persist in the environment for an extended period, PHBV can undergo microbial degradation, ultimately breaking down into natural compounds.
(4) BUNA-S:
BUNA-S refers to a type of synthetic rubber, specifically styrene-butadiene rubber (SBR). Styrene-butadiene rubber is widely used in the production of tires, conveyor belts, and various rubber products. Like neoprene, SBR is not biodegradable.
In summary, PHBV is the biodegradable synthetic polymer among the options provided. The development and use of biodegradable polymers like PHBV aim to address environmental concerns associated with the accumulation of non-biodegradable plastics in various ecosystems. | 
