What does receiving both UV exposures achieve?

Exposure to both UVA and UVB rays is fundamental in the tanning process. UVA rays penetrate the skin more deeply and are primarily responsible for stimulating melanocytes, the cells that produce melanin. This process leads to the pigmentation of the skin, resulting in a tan. The presence of melanin not only changes the skin color but also acts as a natural defense mechanism against UV radiation to some extent.

Furthermore, UVB rays contribute to this process by stimulating the production of vitamin D and also play a role in producing an immediate tanning effect. Both UVA and UVB exposures work synergistically to enhance the bronzing effect of the skin, making option C the most appropriate answer.

While skin hydration, protection, and the risk of sunburn are important aspects of skin health, they are not directly achieved through the action of receiving both types of UV exposure in the way that melanin stimulation and bronzing are.