Which function is common to skin, hair, and nails?

Protection from harmful things.

Explanation:

The integumentary system consists of the skin, hair, nails, the subcutaneous tissue below the skin, and assorted glands. The most obvious function of the integumentary system is the protection that the skin gives to underlying tissues.

intimacy, passion and commitment are the components of a interpersonal relationship emphasized in the triangular theory of love by robert sternberg.

the triangular theory of love says love can be comprehend as this componest form the vertices of a triangle.  

intimacy relates to feelings such as of closeness and connection;

passion relates the drives that brings people together, as physical attraction.

commitment relates to the being in a long-term relationship.

c. reserves power to the states and people