What does sebum help to preserve in hair and skin?

Sebum is an oily substance produced by sebaceous glands in the skin and hair follicles. Its primary role is to moisturize and protect the skin and hair by forming a barrier that prevents water loss. This helps maintain the softness and suppleness of both skin and hair, making option B the best choice.

While sebum also contributes to shine by coating hair and skin, its key function is more associated with maintaining softness. It can also play a role in protecting the strength of hair and skin by preventing them from becoming dry and brittle. It is less directly related to preserving color; for instance, sebum does not impact pigmentation or the vibrancy of color in either skin or hair.

Therefore, among the options, softness is the most accurate representation of what sebum helps to preserve.