Due to the Law of Segregation, members of a gene pair must separate into the gametes. Therefore, two a's won't be found in one gamete because they are homologous and will separate into different gametes. Therefore, any combination of letters a, r, or s will work. Due to the Law of Independent Assortment, the genes assort independently of one another into the gametes that are produced. Therefore, ArS, Ars, aRs are correct. Other possiblilities not listed include: arS and ars. Because most organisms have more than three gene pairs, and they can combine in so many ways within the sex cells, this leads to variations not only in various members of a species, but among one's own family.