A black compound ‘A’ in its solid state is fused with KOH and KClO₃. The aqueous extract of the fused mass is a green coloured solution ‘B’. On passing CO₂ gas through it, pink colour of ‘C’ is noticed along with some black insoluble massof ‘A’. The pink coloured solution is decolourised by Fe²⁺ in acidic medium. The oxidation state of the central metal in ‘C’ is?
A +4
B +5
C +6
D +7