When `MnO_2` is fused with KOH in the presence of `KNO_3` 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 acidified solution of compound (B) oxidises KI to (D). Identify A, B, C and D.

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).

When XO_2 is fused with an alkali metal hydroxide in presence of an oxidizing agent such as KNO_3 a dark green product is formed which disproportionates in acidic solution to afford a dark purple solution. Xis:

When an oxide of Mn (A) is fused with KOH in the presence of an oxidizing agent and dissolved in water, it gives a dark solution of compound