Which of the following can be employed for the conversion of potassium manganate to potassium permanganate?
A) Ozone; 

B) Chlorine 

C) Electrolysis

Electrolytic oxidation in alkaline helps in converting potassium manganate to permanganate.

${\mathrm{K}}_2{\mathrm{MnO}}_4 + {\mathrm{H}}_2\mathrm{O} \to {\mathrm{KMnO}}_4 + \mathrm{KOH}$

The chlorination method can be used to convert or oxidize potassium manganate. 

$2{{\mathrm{MnO}}_4}^{2-} + {\mathrm{O}}_3 + {\mathrm{H}}_2\mathrm{O} \to 2{{\mathrm{MnO}}_4}^{-} + 2{\mathrm{OH}}^{-} + {\mathrm{O}}_2$

The Ozonolysis method is similar to the chlorination method as well.

$2{{\mathrm{MnO}}_4}^{2-} + {\mathrm{Cl}}_2 \to 2{{\mathrm{MnO}}_4}^{-} + 2{\mathrm{Cl}}^{-}$

Hence, the correct answer is option (D) All of these.