Which of the following represents redox reactions?
I. Cr2O72−+2OH-⟶2CrO42−+H2OII. Zn+CuSO4⟶ZnSO4+CuIII. 2MnO4⊖+3Mn2++4OH-⟶5MnO2+2H2OIV. 2Cu⊕⟶Cu+Cu2+
I, II
I, III
III, IV
II, III, IV
II, III and IV are redox reactions , and involves change in oxidation states