The polymer, which can be stretched and retains its original status on releasing the force is

To determine which polymer can be stretched and returns to its original shape when the force is released, one must consider the property called elasticity; polymers exhibiting this behavior are known as elastomers. Nylon-6,6 is a polyamide (fibre) characterized by strong intermolecular hydrogen bonding and high tensile strength. Its structural features make it a fibre rather than an elastomer. Terylene is a polyester fibre made from ethylene glycol and terephthalic acid. Its properties align with those of a fibre, not an elastomer. Bakelite is a phenol-formaldehyde thermosetting plastic with extensive cross-linking, resulting in a hard, rigid material that cannot be stretched.

Buna-N, a copolymer of 1,3-butadiene and acrylonitrile, is a synthetic rubber with weak intermolecular forces and a cross-linked network. These characteristics allow it to stretch easily and then recover its original shape once the force is removed, qualifying it as an elastomer. Hence, the correct answer is Option B: Buna-N.