Context: In a group of fruit flies, some individuals have a gray body and others have a black body. In this group, the gene for the body color trait has two alleles. The allele B is for a gray body, and the allele b is for a black body.
A certain fruit fly from this group has a black body. This fly has two alleles for a black body.
Based on this information, what is this fruit fly's phenotype for the body color trait?
A. a black body
B. bb
Identify the correct choice from the options below and respond with the letter of the correct option.

A