The "tanning" effect, which is darkening of the skin, that occurs when a person is exposed to the sun is due to melanin. The Option A.
Melanin is a complex molecule leading to different skin colors and tanning abilities. Melanin is the primary pigment responsible for skin coloration.
When the skin is exposed to ultraviolet (UV) rays from the sun, it triggers the production of melanin in special cells called melanocytes. Melanin acts as a natural defense mechanism to protect the skin from the harmful effects of UV radiation.
It absorbs the UV rays and dissipates the energy as heat, preventing it from damaging the DNA in skin cells. As a result, the skin darkens or tans as a way to shield itself from further UV damage.