Which statement correctly contrasts the bleaching action of moist $Cl X_{2}$ and moist $SO X_{2}$ ?

A $Cl X_{2}$ bleaches by oxidation and the effect is permanent; $SO X_{2}$ bleaches by reduction and the colour returns on exposure to air
BBoth bleach by oxidation and both effects are permanent
C $Cl X_{2}$ bleaches by reduction and $SO X_{2}$ by oxidation
DBoth bleach by reduction and both effects are temporary

Answer: A

Moist

Cl X_{2}

forms

HOCl

, which gives nascent oxygen and oxidises coloured matter irreversibly.

SO X_{2}

(in water) reduces the dye to a colourless form, and air re-oxidises it, so the colour returns.