Unknown salt $\mathrm{A}+\text{ solid }{\mathrm{K}}_2{\mathrm{Cr}}_2{\mathrm{O}}_7+\text{ conc. }{\mathrm{H}}_2{\mathrm{SO}}_4\to$ Reddish brown fumes.

Which is the correct statement regarding the above observation?

To obtain the solution that confines   ${\mathrm{Cl}}^{-}/\mathrm{Br}$ yellow ${\mathrm{K}}_2{\mathrm{Cr}}_2{\mathrm{O}}_7$ that is used for stewing  ${\mathrm{Cl}}^{-}$ Salts and the fumes  that are passed through an Aqueous $\mathrm{NaOH}$ solution are combined

Hence It neither confirms ${\mathrm{Cl}}^{-}$ or ${\mathrm{Br}}^{-}\text{ion }$ unless it is passed through $\mathrm{NaOH}$ solution