Which of the following materials is classified as a natural polymer?

Natural polymers are long‑chain molecules that come directly from living organisms, such as plants, animals, or microorganisms. They are made up of repeating units that are chemically similar to the building blocks used in life, like sugars or amino acids. A common example is cellulose, the fibrous material that gives plants their structure, which is made of glucose units linked together. Because cellulose is produced by plants and not synthetically made, it is a classic natural polymer. This contrasts with synthetic polymers such as polyethylene, which are created in factories from petrochemicals.