What protein protects the inner living skin from the damaging effects of ultraviolet rays?

The correct choice is melanin, as it is the pigment primarily responsible for protecting the skin from the harmful effects of ultraviolet (UV) rays. Melanin absorbs and dissipates UV radiation, which significantly reduces the risk of DNA damage in skin cells that can lead to skin cancer. This protective action helps to shield the skin from sunburn and other adverse effects associated with excessive UV exposure.

In contrast, keratin is a structural protein that provides strength and resilience to the skin, nails, and hair, but it does not directly provide protection against UV radiation. Collagen serves as a foundational protein in the skin, contributing to its firmness and elasticity but also lacks the protective ability against UV rays. Elastin, on the other hand, allows skin to return to its original shape after stretching, thus contributing to skin elasticity without inherent UV protection.