Explain the following in terms of gain or loss of oxygen with two examples of each 

(A) Oxidation (B) Reduction

A. Oxidation reactions can be defined in terms of the addition of oxygen or the removal of hydrogen.

Examples:

CuO(s) + H₂(g) → Cu(s) + H₂O(l)

CuO adds oxygen to H₂, CuO is, therefore, the oxidizing agent or oxidant, it oxidizes the H₂ to H₂O.

 B. Reduction involves a half-reaction in which a chemical species decreases its oxidation number, done usually by gaining electrons.

Example:

CuO(s) + H₂(g) → Cu(s) + H₂O(l)

Oxidation involves the addition of oxygen and reduction involves the removal of oxygen.

Hence option B is correct.