Concept:The mass of an element in a compound is used to find the moles of the compound through its molar proportion.Explanation:Carbon(iv)oxide is CO2.One mole of CO2 contains 2 moles of oxygen atoms.Mass of 1 mole of oxygen atoms is 16.0 g.Therefore, oxygen present in 1 mole of CO2 is 2×16.0=32.0 g.Let x be the moles of CO2 that contain 16.0 g of oxygen.Using proportion: 32.0 g of oxygen is present in 1 mole of CO2.So, 16.0 g of oxygen is present in 32.016.0=0.50 mole of CO2.Answer:D. 0.50 mol