A hydrated metallic salt A, light green in colour, gives a white anhydrous residue B after being heated gradually. B is soluble in water and its aqueous solution reacts with NO to give a dark brown compound C. B on strong heating gives a brown resiodue D and a mixture of two gases E and F. The gaseous mixture, when passed through acidified `KMnO_4` discharges the pink colour, when passed through acidified `BaCl_2` solution, gives a white precipitate. Identifty A, B, C, D, E and F

Explanation

`FeSO_4.7H_2O(A)overset(triangle)toFeSO_4(B)` (White)
`FeSO_4+No overset(H_2O)to[Fe(H_2O)_5NO]SO_4(C)`
`FeSO_4overset(triangle)toFe_2SO_3(D)+SO_3(E)+SO_3(F)`
`SO_2+SO_3+KMnO_4toMn^(2+)` (pink solution)
`SO_2+SO_3+BaCl_2toBaSO_4` (White precipitate)