But if it's either homozygous dominant or heterozygous for D, then because we have the presence of at least one uppercase D, that means we're going to have a darker color. And the type or the shade of the dark color depends on if we have at least one of these uppercase bees. If we don't have an uppercase bees on either one of these two chromosomes, we produce a chocolate color. But if we have at least one uppercase B, so here or here, then we produce a black coat color. So this is an example of epistasis. Why?