Concept:Reduction by carbon or hydrogen works only for oxides of metals that are less reactive than carbon.
Explanation:In the reactivity series, magnesium is above carbon.
This means magnesium holds oxygen more strongly than carbon can remove.
When
MgO is heated with carbon or hydrogen, no reduction to magnesium metal occurs.
Lead, copper, and tin are below carbon in the reactivity series.
Therefore, their oxides, such as
PbO,
CuO, and
SnO, can be reduced to the metals by heating with carbon or hydrogen.
Magnesium oxide is the oxide that is not reduced to the metal under these conditions.
Answer:B. Magnesium oxide