Based on this information, what is Buttons's phenotype for the fur type trait?

 - curly fur
 - straight fur
Buttons's genotype for the fur type gene is ff. Buttons's genotype of ff has only f alleles. The f allele is for curly fur. So, Buttons's phenotype for the fur type trait must be curly fur.
To check this answer, consider whether Buttons's alleles are dominant or recessive. The allele for curly fur (f) is recessive to the allele for straight fur (F). This means F is a dominant allele, and f is a recessive allele.
Buttons's genotype of ff has only recessive alleles. An organism with only recessive alleles for a gene will have the recessive allele's version of the trait. So, Buttons's phenotype for the fur type trait must be curly fur.