Correct Option: D

Human skin colour is primarily due to the presence of melanin in the skin. Skin colour ranges from almost black to white with a pinkish tinge due to blood vessels underneath. Variation in natural skin colour is mainly due to genetics, although the evolutionary causes are not completely certain. Melanin is produced by cells called melanocytes in a process called melanogenesis. Melanin is triggered by an enzyme called tyrosinase, which creates the color of skin, eyes, and hair shades. Melanin controls the amount of ultraviolet (UV) radiation from the sun that penetrates the skin by absorption. While UV radiation can assist in the production of vitamin D, excessive exposure to UV can damage health.