Decide if the following substances are elements, compounds, or mixtures. Au A: Element B: Compound OC: Mixture copper A: Element OB: Compound OC: Mixture salt and pepper A: Element B: Compound OC: Mixture CO A: Element B: Compound C: Mixture sodium metal (Na) A: Element B: Compound C: Mixture hydrogen gas OA: Element B: Compound OC: Mixture Co A: Element B: Compound C: Mixture