Redox reactions play a vital role in chemistry and biology. The values of standard redox potential `(E^(@))` of two half-cells reactions decide which way the reaction is expected to proceed. A simple example is a Daniell cell in which zince goes into solution and copper gets deposited. Given below are set of half-cell reactions (acidic medium ) along with their `E^(@)` in V with respect to normal hydrogen electrode values. `{:(l_(2)+2e^(-)rarr2l^(-),E^(@)=0.54),(Cl_(2)+2e^(-)rarr2Cl^(-)" ",E^(@)=1.36),(Mn^(3+)+e^(-)rarrMn^(2+),E^(2)=1.50),(Fe^(3+)+e^(-)rarrFe^(2+)" ",E^(@)=0.77),(O_(2)+4H^(+)+4e^(-)rarr2H_(2)O,E^(@)=1.23):}` while `Fe^(3+)` is stable, `Mn^(3+)` is not stable in acid solution because :A. `O_(2)`oxidises `Mn^(2+)` to `Mn^(3+)`B. `O_(2)` oxidises both `MN=n^(2+)` and `Fe^(2+)`C. `Fe^(3+)` oxidizes `H_(2)O` to `O_(2)`D. `Mn^(3+)` oxidises `H_(2)O` to `O_(2)`