Which of the following is not an example of oxidation?

The term oxidation was used to describe reactions in which an element combines with oxygen. The oxidation of magnesium and oxygen occurs in the reaction between magnesium metal and oxygen to form magnesium oxide. Rust and the brown colour on a cut apple are examples of oxidation.

Reduction is defined as the removal of oxygen, When copper oxide is converted into copper, oxygen gas is released so it is a reduction process.

Hence, Copper oxide converted into copper is not an example of oxidation.