Which one of the following is a natural polymer?

Silk is the correct answer. It is a natural protein polymer secreted by silkworm larvae (Bombyx mori) as fibroin, a chain of amino acid residues joined by peptide bonds. Natural polymers occur in plants and animals, for example cellulose, starch, proteins and natural rubber (cis-polyisoprene).

• Bakelite is a synthetic thermosetting polymer made by condensing phenol with formaldehyde. Leo Baekeland developed it in 1907, and it was the first fully synthetic plastic.
• Kevlar is a synthetic aramid fibre, poly-paraphenylene terephthalamide, valued for high tensile strength and used in bulletproof jackets. It is man-made.
• Lexan is a trade name for polycarbonate, a synthetic thermoplastic.

The concept links to everyday materials and to Mains GS-III discussions on biodegradable plastics. Natural polymers degrade more readily, which is why cellulose- and protein-based materials get attention in plastic waste debates. Silk also ties into the handloom and sericulture economy.

Trap: aspirants pick Bakelite because it is the oldest well-known plastic and sounds traditional. The age of a material has nothing to do with whether it is natural.