Answer: (C) Copper and silver
According to the textbook, gold, silver, platinum and copper are found in the free state, but copper and silver are also found in the combined state as sulphide or oxide ores.
The key distinction here is "both free state and combined state." Gold and platinum occur only in free (native) state. Copper and silver occur in both — hence option C is correct. This is directly stated in section 3.4.1.