Concept:Gunmetal is an alloy made mostly of copper and tin, with a small amount of zinc.Explanation:The exact composition of gunmetal is about 88% copper, 10% tin, and 2% zinc.Option D (Cu = 90%, Sn = 10%) is the closest match to this standard ratio.Option A has too much tin (40%). Options B and C have copper percentages far from 88%.Therefore, only option D is correct.Answer:D. Cu=90%, Sn=10%