Which was the first metal used?
A) Iron
B) Copper
C) Zinc
D) Gold

Hint: A metal is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well.

Complete answer:
> In the history of mankind, the first metal to be discovered was Copper.
> A metal is a material which when freshly prepared, polished,otherwise fractured, presents a lustrous appearance, and conducts electricity and heat very well. Metals are typically malleable i.e. they can be hammered into thin sheets or ductile i.e. can be drawn into wires. A metal can be a chemical element such as iron: an alloy like stainless steel or even a molecular compound.
> Metals can be categorized according to their physical or chemical properties. In chemistry, a metal is generally regarded as any substance capable of conducting electricity at a temperature of absolute zero.
> Many elements and compounds that are not generally classified as metals become metallic under conditions of high pressures. For example, the nonmetal iodine gradually becomes a metal at a pressure between 40 and 170 thousand times atmospheric pressure. Equally, a few substances appeared as metals can turn out to be nonmetals.

Therefore, the suitable choice is option (b).

Note: Copper is a chemical element with the symbol Cu and the atomic number 29. It is a soft, malleable and ductile metallic with very excessive thermal and electric conductivity.