Which one of the following is a redox reaction?
A) 2Na(g) + Cl₂(g) → 2NaCl(s)
B) Ba²⁺(aq) + SO₄²⁻(aq) → BaSO₄(s)
C) K₂Cr₂O₇(aq) + 2KOH(aq) → 2K₂CrO₄(aq) + H₂O(l)
D) Na₂CO₃(s) + 2HCl(aq) → 2NaCl(aq) + CO₂(g) + H₂O(l)
E) H₂O(l) → H⁺(aq) + OH⁻(aq)
Answer: A