A mixture upon adding cone. ${\mathrm{H}}_2{\mathrm{SO}}_4$ gives deep red fumes. It may contain the anions pair:

${\mathrm{Cr}}_2{\mathrm{O}}_7^{2-}$ and  ${\mathrm{Cl}}^{-}$ mixture upon adding concentrated sulphuric acid gives deep red fumes.

The reaction Is as follows,

$4{\mathrm{Cl}}^{-}+{\mathrm{Cr}}_2{\mathrm{O}}_7^{2-}+6{\mathrm{H}}^{+}\to 2{\mathrm{CrO}}_2{\mathrm{Cl}}_2\uparrow \text{ (deep red) }+3{\mathrm{H}}_2\mathrm{O}$

Then, the mixture is added cone.${\mathrm{H}}_2{\mathrm{SO}}_4$ gives deep red fumes.

The option is ${\mathrm{Cr}}_2{\mathrm{O}}_7^{2-}$ and ${\mathrm{Cl}}^{-}$.