A white solid is first heated with dil. ${\mathrm{H}}_2{\mathrm{SO}}_4$ and then with conc. ${\mathrm{H}}_2{\mathrm{SO}}_4$. No action was observed in either case. The solid salt contains :

Heat is applied to a white solid using both concentrated and diluted . In these scenarios, no change is observed because the solid contains sulphates.

Barium chloride solution reacts with solutions containing sulphate ions to form a white precipitate of barium sulphate.

For example, ${\mathrm{Na}}_2{\mathrm{SO}}_4+{\mathrm{BaCl}}_2\to 2\mathrm{NaCl}+{\mathrm{BaSO}}_4\downarrow$ $\text{ (whiteppt) }$

So, the correct option is D.