A substance on treatment with dilute `H_(2)SO_(4)` liberates a colourless gas which produces `(I)` turbidity with baryta water and `(ii)` turns acidified dichromate solution green. The reaction indicates the presence of `:`
A. `CO_(3)^(2-)`
B. `S^(2-)`
C. `SO_(3)^(2-)`
D. `NO_(2)^(-)`
