From the reactions below, select the one that is a redox reaction.

• A. 2 KOH(aq) + CO₂(g) → K₂CO₃(aq) + H₂O(l)
• B. 2 Al(s) + Fe₂O₃(s) → Al₂O₃(s) + 2 Fe(s)
• C. HClO₄(aq) + RbOH(aq) → RbClO₄(aq) + H₂O(l)
• D. CaS(aq) + 2 HNO₃(aq) → Ca(NO₃)₂(aq) + H₂S(g)

Answer: (B)