If is reduced by oxalic acid in an acidic medium, then oxidation number of Mn changes from
4 to 2
6 to 4
7 to 2
7 to 4
Oxalic acid reacts with acidified and gets oxidised to
reducing the permanganate ions to
. The reaction is given as
So, the oxidation state of Manganese changes from +7 to +2.
Therefore, option (3) is correct.