Concept:Identify the pair in which both substances can be further oxidized by oxygen to higher oxides.Explanation:SO2 reacts with oxygen to form sulfur trioxide:2SO2+O2→2SO3NO reacts with oxygen to form nitrogen dioxide:2NO+O2→2NO2The other options contain substances like CO2 and H2O, which are already fully oxidized or cannot readily form higher oxides with oxygen.Answer:D. SO2 and NO