Context: This passage describes the shell banding trait in Cepaea snails:

In a group of Cepaea snails, some individuals have a banded shell and others have an unbanded shell. In this group, the gene for the shell banding trait has two alleles. The allele B is for a banded shell, and the allele b is for an unbanded shell.
A certain Cepaea snail from this group has a banded shell. This snail has two alleles for a banded shell.
Based on this information, what is this Cepaea snail's phenotype for the shell banding trait?
A. BB
B. a banded shell
From the given choices, select the correct answer and reply with the letter of the chosen option.

B