The correct option is C mixed salt
Mixed salt : A mixed salt contains more than one cation or an ion other than hydrogen (H+) or hydride (H−) ions. Bleaching powder, CaOCl2, is a mixed salt since though it contains only one cation (Ca2+), it also contains two anions Cl− and OCl−.
Bleaching powder is a yellowish white powder prepared by passing chlorine gas over dry slaked lime.
Ca(OH)2+Cl2→CaOCl2+H2O