The standard reduction potential of Cu²⁺/Cu is 0.34 and is a positive value. The value lies higher than the potential of hydrogen electrode. The reduction potential value being higher than hydrogen is a stronger oxidizing agent than H⁺/H₂. It also means that it is more stable when reduced i.e. more stable on gaining electrons. They get more easily reduced than hydrogen ions. This also means hydrogen ions cannot oxidize Cu, alternatively hydrogen gas can reduce copper ion. The reverse cannot occur, hence Cu cannot reduce H⁺. Options (ii) and (iv) are correct.