A pale green crystalline metal salt of M dissolves freely in water. It gives a brown precipitate on addition of aqueous NaOH. The metal salt solution also gtives a black precipitate on bubbling `H_2 S` in aqueous medium. An aqueous solution of the metal salt decolourizes the pink colour of the premanganate solution. The metal in the metal salt solution is

Options

A. copper
B. Aluminium
C. Lead
D. Iron

Explanation

Pale green salt contain a mixture of `Fe^(2+)` and `Fe^(3+)` ions.
`Fe^(3+) +3OH^(-) to underset("Brown ppt.")(Fe(OH)_(3)`
`Fe^(2+) +S^(2-) to underset("Brown ppt.")(FeS)`
`Fe^(2+)` reduces `KMnO_(4)` discharging its pink colour.