Think about which metal is easiest to get out of the ground and work with using only fire and simple tools, no advanced smelting.
- Copper is often found in a native, nearly pure state in nature and melts at a comparatively low temperature.
- Early humans could heat copper ore in a simple fire and hammer or cast the metal into tools and ornaments, which is why the era right after the Stone Age is named the Copper Age.
- Bronze needed copper to be alloyed with tin, so bronze use necessarily came after copper was already known, it cannot be the first metal.
- Iron requires very high furnace temperatures to separate it from its ore, a technology that developed much later, giving the later Iron Age its name.
- Gold was used mainly for decoration in small quantities and did not become the everyday working metal that copper did.
So the timeline places copper first among these options, making option B correct.