Context: This passage describes the Bekko patterning trait in koi fish:

In a group of koi fish, some individuals have Bekko patterning and others do not. In this group, the gene for the Bekko patterning trait has two alleles. The allele for not having Bekko patterning (b) is recessive to the allele for having Bekko patterning (B).
Undyne is a koi fish from this group. Undyne has the homozygous genotype BB for the Bekko patterning gene.
Based on this information, what is Undyne's phenotype for the Bekko patterning trait?
A. not having Bekko patterning
B. having Bekko patterning
Answer with the option's letter from the given choices directly.
Answer: B