Which of the following is an example of a natural fiber?

Wool is considered a natural fiber because it is derived directly from the fleece of sheep and other animals. Natural fibers come from plants or animals and are characterized by their ability to biodegrade and their generally lower environmental impact compared to synthetic fibers. Wool is not only warm and insulating, but it also has moisture-wicking properties, making it suitable for various clothing applications.

On the other hand, the other options listed—polyester, nylon, and acrylic—are synthetic fibers. These materials are created through chemical processes and do not have the same biological origins as natural fibers like wool. They are derived from petroleum products and are engineered to mimic some of the properties of natural fibers but lack the same environmental sustainability.