Bleaching powder, $Ca (OCl) Cl$ , releases chlorine on treatment with dilute acid. This happens because

A $OCl X^{-}$ disproportionates to $Cl X_{2}$ and $O X_{2}$
Bthe acid oxidises $Cl X^{-}$ and $OCl X^{-}$ separately to $Cl X_{2}$
C $OCl X^{-}$ (+1) and $Cl X^{-}$ (-1) react to give $Cl X_{2}$ (0) in a comproportionation
D $OCl X^{-}$ is reduced to $Cl X^{-}$ only, and the acid is oxidised

Answer: C

In acid,

OCl X^{-} + Cl X^{-} + 2 H X^{+} \to Cl X_{2} + H X_{2} O

. Chlorine at +1 is reduced to 0 and chlorine at -1 is oxidised to 0, so both pathways converge to

Cl X_{2}

. It is the reverse of the disproportionation of

Cl X_{2}

in alkali.