In which conversion is the transition metal oxidised?
MnO4−→Mn2+\text{MnO}_4^{-} \rightarrow \text{Mn}^{2+}MnO4−→Mn2+
VO2+→VO2+\text{VO}_2^{+} \rightarrow \text{VO}^{2+}VO2+→VO2+
Cr3+→CrO42−\text{Cr}^{3+} \rightarrow \text{CrO}_4^{2-}Cr3+→CrO42−
MnO42−→MnO2\text{MnO}_4^{2-} \rightarrow \text{MnO}_2MnO42−→MnO2