Compound A undergoes the following reaction to form B and C:
\[
\text{KNO}_3 + \text{KOH} \to \text{Black coloured solid} (A) \xrightarrow{\text{heated}} \text{Green coloured solid B} + \text{Pink solution + A} (\text{C decolorised by Fe}^{2+})
\]
Identify A, B, and C respectively