During the reaction of solid sodium bromide with concentrated sulfuric acid, a mixture of gases and vapours is evolved. One of these gaseous products, Gas XXX, is a choking, colourless gas that turns moist blue litmus paper red, and turns a filter paper soaked in acidified potassium dichromate(VI) from orange to green.
Which of the following is Gas XXX?
HBr\text{HBr}HBr
SO2\text{SO}_2SO2
Br2\text{Br}_2Br2
H2S\text{H}_2\text{S}H2S