Q. A white crystalline salt A reacts with dilute HCI to liberate a suffocating gas B and also forms a yellow precipitate. The gas B turns potassium dichromate acidified with dilute H2SO4 to a green coloured solution C. A, B and C are respectively ______?

1. Na2S2O3, SO2, Cr2 (SO4)3
2. Na2SO3, SO2, Cr2 (SO4)3
3. Na2SO4, SO2, Cr2 (SO4)3
4. Na2S, SO, Cr2 (SO4)3