Need ! : the color pattern is species of duck is determined by a single pair of genes with three alleles. the d(h) and d(r) alleles are codominant, while d allele is recessive to both. how many phenotypes are possible in a group of ducks that contain all of the possible combinations of alleles?

In an inheritance pattern of codominance, we can see many phenotypes. We should begin by listing all the possible genotypes and associated genotypes: 
Genotypes                  Phenotypes
D(H) D(H)                      H
D(H) D(R)                      HR
D(H) d                            H
D(R) D(R)                      R
D(R) d                            R
d d                                  d

If we look at the phenotypes, there are two ways to get the "H" phenotype, two ways to make the "R" phenotype, one way to make the "HR" phenotype. and one way to make the "d" phenotype. That means there are four separate phenotypes possible.