The correct option is D Potassium permanganate
Acidified potassium permanganate is used to test the presence of SO2. A filter paper or cotton wool dipped in acidified KMnO4 is held over the gas, the former decolorizes, confirming the presence of gas.
2MnO4−+5SO2+2H2O→5SO2−4+2Mn2++4H+