In humans blood type is determined by the A, B, and O alleles. The A and B alleles are codominant to each other and dominant over the O allele. An individual with the AO genotype and an individual with the BO genotype can produce offspring with which of the following phenotypes?
1.) A, B, or O only
2.) A or B only
3.) A, B, AB or O
4.) O only
