To determine which fiber is obtained from plants, we need to evaluate each option based on its source:
Silk: Silk is an animal-based fiber. It is produced by silkworms during the construction of their cocoons. Thus, this fiber is not obtained from plants.
Wool: Wool is derived from the fleece of sheep and sometimes other animals like goats (such as cashmere or mohair). Therefore, wool is also not plant-based.
Cotton: Cotton is a natural fiber that grows in the seedpods, or bolls, of cotton plants. It is a plant-based fiber, used extensively in the textile industry for making clothes and other fabric items. Therefore, cotton is the correct answer.
Leather: Leather is made from animal hide or skin, typically from cows. It is not derived from plants.
Therefore, the only fiber in the provided options that is obtained from plants is Cotton.