Which of the following is NOT a characteristic of natural fibers?

Natural fibers, such as cotton, wool, and silk, are derived from plants and animals and have specific characteristics that set them apart from synthetic fibers. The term "synthetic" refers to fibers that are artificially made through chemical processes, such as polyester or nylon, which do not occur in nature.

Durability is a characteristic of many natural fibers; for example, wool fibers can be quite strong and resilient. Being environmentally friendly is another characteristic since natural fibers are biodegradable and often produced with less environmental impact compared to synthetic options. Breathability, often associated with natural fibers like cotton and linen, allows air circulation, making them comfortable to wear in various climates.

In contrast, synthetic fibers are not a characteristic of natural fibers and are formed in laboratories or factories from petrochemicals, highlighting the clear distinction between the two categories. Hence, identifying "synthetic" as the answer effectively captures the essence of natural fiber characteristics as opposed to those of synthetic fibers.