ANS:B - Zn

Zinc (Zn) is a trace metal that plays a crucial role in the structure and function of insulin. In insulin, zinc ions help stabilize the structure of the hormone, particularly in its storage form within pancreatic β-cells. These zinc ions are critical for the formation of insulin hexamers, which are the storage form of insulin in β-cells. When insulin is released into the bloodstream, it undergoes dissociation into monomers for its biological activity. Furthermore, zinc ions are involved in the regulation of insulin secretion from pancreatic β-cells. They act as cofactors for various enzymes involved in the synthesis, processing, and secretion of insulin. Overall, zinc is essential for the proper structure, storage, and secretion of insulin, making it a critical component for the regulation of blood glucose levels in the body.