The Mound Builders used metal tools, and were probably metal builders. Based on that information I would say the answer is B.Copper, because copper is a metal.
Medium: Any material used to create art.
Proportion: A principle of design that refers to the size relationship of an art work to each other and to the whole.
Technique: The manner in which the artist controls his medium to achieve the desired effect
Answer:
a: foreground
Explanation:
this is where you want the attention of the audience to be so this is your best bet
