ANSWER: (C) Descent groups are permanent, whereas nuclear families are not.
EXPLANATION:
Descent groups refers to a social (kin) group whose linear members (descedant) of a common ancestry background.
However, unilineal descent is referred to as; matrilineal (if traced through the mother's lineage), patrilineal (father’s line based tracing), and bilateral (if traced through both the father and mother lineage).
Whereas, Nuclear family refers to a group of people consisting of two adults (parents) and their children (either biological or adopted). This pairs of adults comes together through ties of partnership and parenthood. Nuclear family has been overtime extended to same sex marriage.
Lastly, from the aforementioned definitions, the decent groups are permanent through statutory lineage while nuclear families are not.