$A$ white crystalline salt $A$ reacts with dilute $HCl$ to liberate a suffocating gas $B$ and also forms a yellow precipitate. The gas $B$ turns potassium dichromate acidified with dilute $H_{2}SO_{4}$ to a green coloured solution $C$. $A$,$B$ and $C$ are respectively

• A
  $Na_{2}SO_{3}, SO_{2}, Cr_{2}(SO_{4})_{3}$
• B
  $Na_{2}S_{2}O_{3}, SO_{2}, Cr_{2}(SO_{4})_{3}$
• C
  $Na_{2}S_{2}, SO_{2}, Cr_{2}(SO_{4})_{3}$
• D
  $Na_{2}SO_{4}, SO_{2}, Cr_{2}(SO_{4})_{3}$