Which of the following metals is least reactive with acids?

Copper is the metal that is least reactive with acids among zinc, iron, aluminium, and copper. In the Reactivity Series, metals are ranked based on their ability to lose electrons; copper is positioned below hydrogen, meaning it cannot displace hydrogen from dilute acids like HCl. Zinc, iron, and aluminium are all located above hydrogen in the series, allowing them to react with dilute acids to produce a salt and evolve hydrogen gas. While aluminium is highly reactive, it sometimes appears slow to react initially due to a protective, thin layer of aluminium oxide on its surface.