When `MnO_2` is fused with KOH in the presence of `KNO_2` as an oxidising agent, it gives a dark green compound (A). Compound (A) disproportionates in acidic solution to give purple compound (B). An alkaline solution of compound (B) oxidises KI to compound (C) whereas an acidified solution of compound (B) oxidises KI to (D). Identify (A), (B), (C), and (D).

Explanation

`A=K_(2)MnO_(4)//MnO_(2)^(2-), B=KMnO_(4)//MnO_(4)^(-), C=IO_(3) or KlO_(3), D=l_(2)`