The A, B and O antigens of the human blood system are sugars that can be found on the surface of red blood cells. The alleles A, B and O refer to the variant forms of the proteins (enzymes) that produce the sugar antigens. The O allele enzyme is non-functional, so that the basic sugar antigen is unaltered. The A and B allele enzymes are dominant over the O allele and alter the sugar to produce A and B antigens, respectively. When both the A and B allele enzymes are present (i.e. in an individual of genotype AB), then both A and B antigens are present and the person has a blood group of AB. Because both the A and B antigens are produced, the A and B alleles are referred to as codominant.
Using this information, what are the possible genotypes of people with the following blood groups?