Why were the blue people of Troublesome creek blue

The blue people of Troublesome Creek had methemoglobinemia, a metabolic condition affecting hemoglobin, the four-part protein that carries oxygen bound to an iron atom at each subunit's core. The Fugate family of the Troublesome Creek region of Kentucky is but one example of a genetic disorder, scientifically known as Methemoglobinemia. ... Due to a recessive gene, some members of the Fugate family have a bluish tint to their skin.

Explanation:

what image you forgot to include it.

i think that the best answer would be c.

tell me if im wrong : )