Based on this information, what is Major's phenotype for the horns trait?

 - not having horns
 - having horns
Major's genotype for the horns gene is HH. Major's genotype of HH has only H allelles. The H allele is for not having horns. So, Major's phenotype for the horns trait must be not having horns.
To check this answer, consider whether Major's alleles are dominant or recessive. The allele for not having horns (H) is dominant over the allele for having horns (h). This means H is a dominant allele, and h is a recessive allele.
Major's genotype of HH has two dominant alleles. An organism with at least one dominant allele for a gene will have the dominant allele's version of the trait. So, Major's phenotype for the horns trait must be not having horns.