When compound (A) is treated with conc. `H_(2)SO_(4)`, a reddish brown colour gas (B) is evolved. To this solution, a solution of (C ) is added slowly from the side of the test tube, a blue ring is obtained at the junction of two layers due to formation of (D).
Gas (B) may be :
A. `Cl_(2)`
B. `Br_(2)`
C. `I_(2)`
D. `NO_(2)`