ANSWER is Silver.Silver is the least active.The reactivity series helps us to know how metals react.A more reactive metal displaces a less reactive metal from a compound. Some metals are more reactive as compared to others. We arrange them in order of their reactivity in a series that starts with the most reactive. Silver is a GOOD conductor of electricity because of the presence of delocalized ELECTRONS between the layers of metal ions.Thus, it is not highly reactive because a LOT of energy is required to break the metallic bonds within the layers.