Context: This passage describes the iridescent scales trait in bettas:

In a group of bettas, some individuals have mostly iridescent scales and others have mostly plain scales. In this group, the gene for the iridescent scales trait has two alleles. The allele for mostly iridescent scales (I) is dominant over the allele for mostly plain scales (i).
Poseidon is a betta from this group. Poseidon has the homozygous genotype ii for the iridescent scales gene.
Based on this information, what is Poseidon's phenotype for the iridescent scales trait?
A. mostly plain scales
B. mostly iridescent scales
Select the correct answer from the provided options and reply with the letter associated with it.
Answer: A