A redox reaction is:MnO2(s) +4H+ →Mnaq+2+H2O

Explanation

Option A is correctYes, the reaction you have given is a redox reaction. In a redox reaction, there is a transfer of electrons between two species. In this reaction, manganese is oxidized from an oxidation state of +4 in MnO2 to +2 in Mn2+. This means that manganese has lost electrons in the reaction. The hydrogen ions are reduced from an oxidation state of +1 in H+ to 0 in H2O. This means that hydrogen ions have gained electrons in the reaction. The addition of 2 electrons on the left-hand side of the equation represents the reduction of manganese. The balanced equation for the reaction is as follows: MnO2(s) + 4H+ + 2e- → Mn2+ (aq) + H2O The balanced equation shows that the number of electrons lost by manganese is equal to the number of electrons gained by hydrogen ions. This is a requirement for a balanced redox reaction. MnO2 +4H+ →Mn+2+H2O+4 +2In order to balance charge 2 electrons, have to be added on L.H.S.MnO2+4H++2e-→Mn+2+2H2O