Which of the following nutrients is particularly involved in energy metabolism?

Carbohydrates are the primary source of energy for the body and play a crucial role in energy metabolism. When consumed, carbohydrates are broken down into glucose, which is then used by the body's cells to produce energy in the form of adenosine triphosphate (ATP). This process occurs during both aerobic and anaerobic respiration, allowing the body to efficiently utilize carbohydrates for energy during physical activity and daily functions.

Other nutrients listed, such as calcium, vitamin C, and sodium, while important for various bodily functions, do not play a direct role in energy metabolism. Calcium is vital for signal transduction in muscle contraction and nerve function, vitamin C is important for the immune system and collagen synthesis, and sodium is essential for fluid balance and nerve impulses. However, none of these nutrients are specifically associated with the metabolic processes that generate energy. This highlights the unique role of carbohydrates in providing energy, making them the correct choice in the context of energy metabolism.