Ultraviolet light is a mutagen, but humans need some exposure to it in order to synthesize vitamin D3. The amount of ultraviolet light that penetrates the skin depends on the skin's pigmentation: more melanin (skin pigment) means less penetration. Certain mutations result in decreased melanin production. Such mutations:
A)are harmful only if inherited from both parents. B)are beneficial only if inherited from both parents. C)are neutral only if inherited from one parent, not the other. D)may be harmful in one environment and beneficial in another.