Which of these is classified as a natural fiber?

Cotton is classified as a natural fiber because it is derived from the cotton plant's seed fibers. Natural fibers come from plants or animals and have not undergone extensive synthetic processing, which is the case with the other options listed. Nylon and polyester are synthetic fibers made from petrochemicals, which involve chemical processes to create the material. Acrylic, although it mimics some qualities of natural fibers, is also a synthetic fiber produced through chemical reactions. Therefore, cotton stands out as a natural fiber because it is harvested directly from nature without undergoing such synthetic alterations. This characteristic of being sourced from plants contributes to cotton's popularity in textiles, recognized for its breathability, softness, and comfort.