(a) Gold, silver, copper, bronze but not iron
(b) Copper, iron, gold but not bronze
(c) Silver, lead, iron but not gold
(d) Gold, tin, bronze but not copper
(a) Gold, silver, copper, bronze but not iron
(b) Copper, iron, gold but not bronze
(c) Silver, lead, iron but not gold
(d) Gold, tin, bronze but not copper