Concept:An ore is a natural mineral from which a metal can be extracted economically.Graphite is not a metallic ore, so it is the exception.Explanation:Bauxite is the main ore of aluminium.Its composition is Al2O3⋅2H2O.Cuprite is an ore of copper and has the formula Cu2O.Cassiterite is an ore of tin and has the formula SnO2.Graphite is an allotrope of carbon, not a compound containing a metal.Therefore, graphite cannot serve as an ore for metal extraction.Answer:D. graphite