Which One of the Following Reactions Is an Example of an Oxidation-Reduction

Which one of the following reactions is an example of an oxidation-reduction reaction?

A) BaO(s) + CO₂(g) $\rightarrow$ BaCO₃(s)
B) H₂(g) + F₂(g) $\rightarrow$ 2HF(g)
C) CaCO₃(s) $\rightarrow$ CaO(s) + CO₂(g)
D) HCl(aq) + NaOH(aq) $\rightarrow$ NaCl(aq) + H₂O(l)
E) Ba²⁺(aq) + SO₄^2-(aq) $\rightarrow$ BaSO₄(s)