Question

chitin is a polysaccharide found in the exoskeleton of insects. the diagram below shows a chitin monomer.
chitin monomer
to which major category of biological molecules does chitin belong?
proteins, because chitin forms the flexible joints of an insects shell
nucleic acids, because chitin provides the blueprint for insect body plans
lipids, because chitin serves as an insulator from their environment
carbohydrates, because chitin is used for structural support in the insects external skeleton

Explanation:

Chitin is a polysaccharide. Polysaccharides are a type of carbohydrate. Carbohydrates serve various functions including structural support, as is the case with chitin in the insect exoskeleton. Proteins have different functions like catalysis and transport, nucleic - acids store genetic information, and lipids are for energy storage and insulation in different contexts.

Answer:

D. carbohydrates, because chitin is used for structural support in the insect's external skeleton