The correct option is C Out growth of the testa
Cotton, seed-hair fibre (testa) of a variety of plants of the genus Gossypium, belonging to the Hibiscus or mallow, family (Malvaceae) and native to most subtropical parts of the world.
Cotton is a soft, fluffy staple fiber that grows in a boll, or protective capsule, around the seeds of cotton plants. The fiber is almost pure cellulose. Under natural conditions, the cotton bolls will tend to increase the dispersion of the seeds. So, fibres of Gosssypium are out growth of testa and not out growth of pericarp, pappus hair and bast fibres.
Therefore, the correct answer is option C.