A white precipitate was formed when BaCl$$_2$$ was added to water extract of an inorganic salt. Further, a gas 'X' with characteristic odour was released when the formed white precipitate was dissolved in dilute HCI. The anion present in the inorganic salt is:

We need to identify the anion in an inorganic salt based on the described test results. When BaCl₂ is added to the water extract of the salt, a white precipitate forms, indicating the presence of an anion that forms an insoluble barium salt. Possible candidates are SO₄²⁻ (BaSO₄ — white), SO₃²⁻ (BaSO₃ — white) and CO₃²⁻ (BaCO₃ — white). The white precipitate dissolves in dilute HCl with the release of a gas X having a characteristic odour. BaSO₄ does not dissolve in dilute HCl, so SO₄²⁻ is ruled out. BaSO₃ dissolves in dilute HCl releasing SO₂, which has a suffocating, pungent odour: $$\text{BaSO}_3 + 2\text{HCl} \rightarrow \text{BaCl}_2 + \text{H}_2\text{O} + \text{SO}_2 \uparrow$$ BaCO₃ also dissolves in HCl but releases CO₂, which is odourless.

The evolution of a gas with a characteristic pungent odour thus confirms the presence of the SO₃²⁻ anion. The answer is Option B: SO₃²⁻.