Which of the following metals is least likely to corrode in moist air?

Copper is a relatively noble metal; its standard electrode potential is high, so it oxidises far less readily than iron, zinc or magnesium. In moist air, copper quickly develops a thin, adherent patina (basic copper carbonate) that seals the surface and blocks further corrosion. By contrast, iron forms porous rust that flakes off, while magnesium and zinc are much more reactive and corrode faster despite their oxide films.