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

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