Concept:Duralumin is a lightweight alloy whose main components are aluminum and copper, with small amounts of other metals added to improve strength.Explanation:Duralumin contains about 90% aluminum and 4% copper.The remaining composition includes small amounts of magnesium and manganese.These added metals give the alloy greater strength and hardness while keeping it light.Therefore, the two additional metals that complete the composition are manganese and magnesium.Answer:D. Manganese and Magnesium