A scalet compound A is treated with concenbtrated `HNO_(3)`to gave a chocolate brown precipitate B. The precipitate is filtered and the filtrate is neurralised with NaOH Addition of KI to the resulting solution gives a yellow precipitate C the brown precipitate B on warming with concentrated `HNO_(3) `in the presence of `Mn(NO_(3))_(2)` produces a pink coloured solution due to the formation of D identify A, B,C, and D write the reaction sequence.