What effect can radiation exposure above 300 rad have on the skin?

Radiation exposure above 300 rad can lead to significant damage to the skin, which includes permanent hair loss and desquamation. At this level of exposure, the radiation can affect the basal layer of the skin where hair follicles are located, ultimately leading to hair loss that may be irreversible. Additionally, high doses of radiation can cause severe damage to the skin cells, resulting in desquamation, which is the shedding or peeling of the outer layer of skin. This occurs as the skin cell turnover is disrupted, and the damaged skin cannot regenerate properly.

In contrast, the other options reflect effects that are not typically associated with such high radiation exposure. Melanin production activation may occur in lower doses as a defense mechanism against radiation damage, but this is not the primary response at high doses. Decreased sensitivity might suggest nerve damage, which is not a direct effect of radiation exposure to the skin at this level. Increased elasticity is unlikely, as radiation tends to damage collagen and elastin fibers, leading to reduced skin elasticity rather than an enhancement.