The correct answer is (b), seed. Cotton fibers are the soft, fluffy substance that surrounds the seeds of the cotton plant. They are made of cellulose, a type of plant fiber that is also found in wood and paper. Cotton fibers are used to make a variety of products, including clothing, bedding, towels, and other textiles.
(a) Leaves: Leaves are the green, flat parts of a plant that absorb sunlight and use it to make food. They are not made of cotton fibers.
(c) Stem: The stem is the main support structure of a plant. It is not made of cotton fibers.
(d) Root: The root is the part of a plant that grows underground and absorbs water and nutrients from the soil. It is not made of cotton fibers.