A scarlet compound A is treated with conc. ${\mathrm{HNO}}_3$ to give a chocolate brown precipitate B. The precipitate is filtered and the filtrate is neutralized with NaOH. Addition of KI to the resulting solution gives a yellow precipitate C. The precipitate B on warming with conc.${\mathrm{HNO}}_3$ in the presence of $\mathrm{Mn}{\left({\mathrm{NO}}_3\right)}_2$ produce a pink-coloured solution due to the formation of D. Correct statement(s) regarding A to D is/are