Which Fitzpatrick skin type is least likely to tan and most likely to burn?

Fitzpatrick skin type I is characterized by very fair skin that often has freckles and rarely tans. Individuals with this skin type typically have light-colored eyes (blue or green) and light hair (blonde or red). Due to the lack of melanin, which provides some protection against UV radiation, people with this skin type are extremely sensitive to sunlight and are at a high risk of sunburns.

This sensitivity means that when they are exposed to UV radiation, they tend to burn quickly without developing a tan. The other skin types, such as II, III, and IV, have progressively more melanin, which provides greater protection against UV rays, allowing for more tanning and less likelihood of burning compared to type I. Thus, skin type I is indeed the correct choice for being the least likely to tan and the most likely to burn.