Natural thermoplastic resin from animal origin: identify the only widely recognized natural thermoplastic that is a product of animal life.

Introduction / Context:
Most thermoplastics are synthetic, but a few natural resins soften upon heating and can be reworked. Distinguishing plant exudates from animal-derived resins is a common exam theme in materials and surface-coatings curricula.

Given Data / Assumptions:

• Shellac is secreted by the lac insect and refined into flakes.
• Rosin, amber, and copal are plant-derived (exudates or fossil resins).

Concept / Approach:
Shellac is the only option listed that is produced by an animal (lac insect). In flake form, it can be dissolved in alcohols for coatings and can also soften with heat, so it is treated as a natural thermoplastic resin. The others come from trees or fossilised resin and are not of animal origin.

Step-by-Step Solution:

Verification / Alternative check:
Coatings handbooks describe shellac as a natural resin from Kerria lacca, widely used historically in varnishes and food/medical glazing.

Why Other Options Are Wrong:

• Rosin/amber/copal/lacquer gums: plant or fossil resins, not animal products.

Common Pitfalls:
Assuming all natural resins are plant-derived; shellac is the key exception.

Final Answer:
Shellac