Which of the following provides natural protection against sunburn through pigmentation?

The correct choice, melanin, is a pigment found in the skin that plays a crucial role in protecting against ultraviolet (UV) radiation from the sun. When skin is exposed to sunlight, melanin is produced by melanocytes to absorb and dissipate UV rays, helping to prevent damage to the skin cells that could lead to sunburn and other harmful effects such as skin cancer. This natural pigmentation not only gives skin its color but also acts as a biological shield, making it an essential component of the body's defense against sun exposure.

Carotene, while it is a pigment that can contribute to skin color, primarily comes from dietary sources such as carrots and other vegetables and does not provide significant protection against UV radiation. Collagen, on the other hand, is a protein that contributes to skin structure and elasticity but does not play a direct role in UV protection. Keratin is a structural protein found in the skin, hair, and nails, providing strength and resilience, but similarly to collagen, it does not serve as a protective pigment against sunburn.