What is the primary function of vitamin B2 (riboflavin) in the human body?

The primary function of vitamin B2, also known as riboflavin, is to enable energy release from macronutrients. Riboflavin plays a crucial role in the body's energy production processes by acting as a coenzyme in the metabolism of carbohydrates, fats, and proteins. It is involved in various enzymatic reactions, such as those needed for the conversion of these macronutrients into ATP (adenosine triphosphate), which is the energy currency of the cell.

While riboflavin contributes to several other bodily functions, including supporting healthy skin and promoting immune function, these are secondary roles compared to its fundamental importance in energy metabolism. Therefore, the correct answer highlights the essential role of riboflavin in ensuring that the body efficiently converts food into usable energy.