Which of these groups is a well-known example of historic polyculture of plants?

Polyculture is a form of agriculture in which more than one species is grown at the same time and place. It is advantageous beacause of its ability to control pests, weeds and disease without major chemical inputs. In polyculture of onion and carrot, onion-smell puts off carrot root fly and vice-versa. A well-known example of historic polyculture is the intercropping of maize, bean and squash plants in a group often referred to as ''the three sisters''. In this combination, the maize provides a structure for the bean to grow on, the bean provides nitrogen for all of the plants, while the squash suppresses weed on the ground. Maize, also known as corn, is a cereal grain. A bean is the seed of one of legume, pea or bean family. The squash (pumpkin or gourd) is a genus of herbaceous vines.

Around 15% to 20% of world's agriculture is estimated as relying on traditional polyculture systems. The intercropping is particularly useful in plots with limited land availability. The lack of concentration of a single crop makes polycultures less appealing to pests who have a strong preference towards a specific crop. As such polycultures consequently experience lower yeild loss than monocultures do. Also, different plants are susceptible to different diseases which leads to a decreased severity of disease.