Which of the following is an essential mineral?

Zinc is classified as an essential mineral because it plays a crucial role in numerous biological functions within the body. It is vital for the proper functioning of the immune system, the synthesis of proteins and DNA, and wound healing. Zinc also contributes to cell division and helps in the production of enzymes that facilitate various metabolic processes. This mineral must be obtained from dietary sources, as the body does not store it in large amounts, making it essential for maintaining health.

Other choices also consist of essential minerals but may not fit the definition of "essential" as precisely in the context of daily intake or specificity. Sodium and chloride are important for fluid balance and nerve function, while iodine is critical for thyroid function. However, the question emphasizes the specific categorization of zinc as essential due to its widespread roles in health and wellness.