What effect does UV radiation have on the skin?

The correct choice highlights the significant adverse effects of UV radiation on the skin. UV radiation can penetrate the skin and lead to cellular damage, which manifests as sunburn, accelerated skin aging (such as wrinkles and loss of elasticity), and an increased risk of skin cancers, including melanoma. The skin's DNA can be altered by the harmful effects of the sun's rays, leading to mutations over time. This cellular damage not only contributes to visible aging but also poses serious health risks, making protection against UV radiation essential for maintaining skin health and preventing skin cancers.

The other options do not accurately reflect the effects of UV radiation. For instance, while collagen production is vital for skin elasticity and youthfulness, UV exposure actually has a damaging effect on collagen fibers, decreasing their integrity rather than increasing production. Additionally, improving skin hydration levels is contrary to the drying effects that UV exposure can have on the skin. Furthermore, while UV radiation can impact hair, in general terms, it does not effectively stimulate hair growth; rather, excessive UV exposure can lead to hair damage and loss.