A student placed an iron nail in blue copper sulphate solution and said, “Copper is more reactive than iron, so copper gets deposited on the nail.” Which is the correct correction to this statement?

Correct answer: Iron is more reactive than copper; therefore, iron displaces copper from copper sulphate.

The governing rule is that a more reactive metal displaces a less reactive metal from its salt solution. Iron is above copper in the reactivity series, so iron atoms enter solution as iron(II) ions while copper ions gain electrons and deposit on the nail: Fe + CuSO₄ → FeSO₄ + Cu. The blue solution may become pale green. Hence option A corrects the statement; this is a displacement reaction, not decomposition.