Question

Sol. Key concept: Chitin is a nitrogen-containing structural polysaccharide.

Chitin is built from repeating N-acetyl-D-glucosamine units joined mainly by β(1→4) linkages. The acetamido group of each repeating unit contains nitrogen. Chitin forms an important part of arthropod exoskeletons and fungal cell walls.

Inulin is a fructan and contains no nitrogen. Trehalose is a non-nitrogenous disaccharide. Hyaluronic acid does contain nitrogen-containing sugar units, but it is not the abundant structural polymer intended here.

Correction / clarification: Chitin is generally described as the second most abundant natural polysaccharide, after cellulose, and as the most abundant nitrogen-containing polysaccharide. The claim “most abundant biopolymer on earth” is incorrect without qualification. Option (c) is the intended answer.