How is a blended family formed?

A、Ablendedfamilyisformedbytwosingle-parentfamily.
B、Ablendedfamilyisformedbyanuclearfamilyandagrandparent.
C、Ablendedfamilyisformedbyanuclearfamilyandgrandparent.
D、Ablendedfamilyisformedbytwofatherlessfamily.