Which of the following compound(s) gives green solution, when treated with ${\mathrm{K}}_2{\mathrm{Cr}}_2{\mathrm{O}}_7$ and dilute ${\mathrm{H}}_2{\mathrm{SO}}_4$?

Sulfites produce SO₂ gas, which smells of burning sulfur, when treated with dilute acid. They turn acidified K₂Cr₂O₇ from orange to green because of reduction of chromium ion(in dichromate solution) to +3 oxidation state.

Acidified K₂Cr₂O₇ solution turns green when ${\mathrm{Na}}_2{\mathrm{SO}}_3$ is added to it. This is due to the formation of ${\mathrm{Cr}}_2{\left({\mathrm{SO}}_4\right)}_3$.

${\mathrm{K}}_2{\mathrm{Cr}}_2{\mathrm{O}}_7+3{\mathrm{Na}}_2{\mathrm{SO}}_3+4{\mathrm{H}}_2{\mathrm{SO}}_4\to {\mathrm{Cr}}_2{\left({\mathrm{SO}}_4\right)}_3+{\mathrm{K}}_2{\mathrm{SO}}_4+3{\mathrm{Na}}_2{\mathrm{SO}}_4+4{\mathrm{H}}_2\mathrm{O}$.

Hence, the correct options are (b, d).