In some aliens, one center horn (A) is codominant with two horns (B). If an alien inherits both alleles, then the alien has three horns. A recessive allele (O) results in an alien which has no horn. Which of the genotypes and phenotypes of the four aliens below is correctly matched?
A. AA – no horn C. OO – two horns
B. BB – one horn D. AB – three horns