Polygenic traits are characters whose phenotypes are influenced by two or more genes. These traits are displayed in continuous distribution. These characters generally have two alleles of each gene but can have multiple alleles too.
Height is also a polygenic trait in humans. Humans can be of different sizes. It is controlled by three genes and six alleles. Eye color, skin color and other traits also polygenic traits in humans.
Thus, the correct answer would be two or more genes.
To get more involvement in a community clean-up project you could make posters and put them around town and you could tell your friends about the project.
