Which from following polymers is classified as fibre?

Polymers are classified based on intermolecular forces and physical properties:

Fibres exhibit high tensile strength and modulus due to strong intermolecular forces like hydrogen bonding or dipole–dipole interactions, enabling dense chain packing.

$\text{Nylon 6,6}$ is a polyamide with strong hydrogen bonding between chains, providing the characteristic tensile strength and elasticity required for fibres.

$\text{Urea formaldehyde resin}$ is a rigid thermosetting plastic, $\text{polystyrene}$ a thermoplastic, and $\text{neoprene}$ an elastomer—none exhibit the structural properties of fibres.

Thus, $\text{Nylon 6,6}$ is correctly classified as a fibre.

The final answer is $\boxed{A}$.