Silver nitrate solution when added to a colorless aqueous solution E forms a white precipitate which dissolves in excess of E. If the white precipitate is heated with water it turns black and the supernatant solution gives a white precipitate with acidified barrum nitrate solution. Therefore, E is :
A. `Na_(2)S`
B. `Na_(2)S_(2)O_(3)`
C. `Na_(2)SO_(3)`
D. `Na_(2)SO_(4)`