Which of the following is NOT a function of the skin?

The correct answer is that respiration is not a function of the skin. The skin serves various critical functions, including secretion, which involves the production and release of substances such as oils and sweat; excretion, which is the removal of waste products from the body through sweat; and protection, which shields the internal organs and tissues from environmental damage, pathogens, and physical injury.

In contrast, the term "respiration" typically refers to the process of gas exchange that occurs primarily in the lungs, involving the intake of oxygen and the release of carbon dioxide. While the skin does play a minor role in gas exchange through processes like transpiration, it is not considered a primary organ for respiration. This distinction clarifies why respiration does not belong to the core functions of the skin, making it the correct choice in this context.