Explanation:

- Non-Unilineal descent: This is a system where descent is traced through both the mother's and the father's lineage, without exclusive preference to either side.

- Option 1 - Agnatic system: This is also known as patrilineal descent, where lineage is traced exclusively through the father's side.

- Option 2 - Cognatic system: This is a non-unilineal system where descent can be traced through both the mother and father's lines.

- Option 3 - Bignatic system: The term "bignatic" is not commonly used in anthropology to describe descent systems. It seems to be a misnomer.

- Option 4 - None: This would be applicable if no listed options were correct, but in this context, option 2 is correct.