Which of the following reactions represents a redox reaction?
A. KOH(aq) + HNO3(aq) → KNO3(aq) + H₂O(1)
B. 2 AgNO3(aq) + Mg(s) 2 Ag(s) + Mg(NO3)2(aq)
C. H₂SO4(aq) + 2 NaOH(aq) → Na2SO4(aq) + 2 H₂O(1)
D. CaCl₂(aq) + Fe(OH)2(aq) → Ca(OH)2(aq) + FeCl2(aq)