Explanation:

- Primary group: These are small, close-knit, and personal groups like families or close friends. They are not always based on ancestry.

- Secondary group: These are larger, more impersonal groups formed around a task or goal, such as a workplace or club.

- In-group: A group that someone identifies with and feels loyalty toward. It isn’t necessarily based on ancestry.

- Descent group: Correct Answer. This is a group whose members are related by common ancestry, tracing lineage through either the mother's or father's line.