Componds `(A)` and `B` are treated with dilute `HCl` separately. The gases liberated are `Y` and `Z` respectively. `Y` turns acidified `K_2 Cr_2 O_7` paper green while `Z` turns lead acetate paper black. The compounds `A` and `B` are respectively :
A. `Na_(2)S " and " Na_(2)SO_(3)`
B. `Na_(2)SO_(3) " and " Na_(2)S`
C. `NaCl " and" Na_(2)CO_(3)`
D. `Na_(2)SO_(3) " and " na_(2)SO_(4)`