Answer:
a. BB
b. bb
C. Bb
Explanation:
As stated in the statement of the question, there is a species of fish in which those with the blue scale, and therefore the blue fish, have the pair of "BB" alleles, while the fish with red scales, and therefore, red fish, has the "bb" allele pair. The crossing between these fish results in a completely heterozygous, hybrid offspring. Since each member of the offspring receives an allele from each parent, the members of the offspring will present the "Bb" alleles.
However, the "BB" and "bb" alleles have codominance, which is an interaction between the alleles, where they do not establish dominance and end up being expressed together, allowing individuals to present both phenotypes at the same time. Thus, in this species of fish, the members with the "Bb" alleles have a patchwork of blue and red scales.