Identify the principal chemical component of cotton fibre used in textiles and medical gauze.

Introduction / Context:
Natural fibres vary in composition. Cotton, derived from the seed hair of the cotton plant, is prized for its cellulosic content which governs dyeing, moisture absorption, and mechanical properties.

Given Data / Assumptions:

• We consider purified fibre (lint) used in textiles.
• Minor constituents (waxes, pectins) are disregarded.

Concept / Approach:
Cotton is composed predominantly of cellulose, a linear polysaccharide of anhydro-glucose units. Lignin is abundant in wood and bast fibres, not in mature cotton lint. Starch and gelatine are unrelated (storage polysaccharide and protein, respectively) and not principal components of cotton fibre.

Step-by-Step Solution:
Recall cotton → nearly pure cellulose after scouring/bleaching.Eliminate lignin (woody tissues), starch (seed/endosperm), gelatine (animal protein).Select cellulose.

Verification / Alternative check:
Textile science references list cotton as ~90%+ cellulose after processing.

Why Other Options Are Wrong:
They are not the dominant chemical component of cotton fibre.

Common Pitfalls:
Confusing lignified bast fibres (e.g., jute) with cotton.

Final Answer:
Cellulose