- Nuclear Family (A): This consists of parents and their children, so the correct characteristic is (II) Mates and their children.
- Matrilineal Descent (B): In this system, kinship is traced through the mother's side, so the characteristic is (IV) Children belong to the kin group of mothers.
- Fraternal Polyandry (C): This is a practice where a woman has multiple husbands, and they are typically brothers, so the correct characteristic is (I) Husbands are Brothers.
- Extended Family (D): An extended family includes parents, children, and other relatives, such as grandparents, aunts, or uncles. The correct characteristic is (III) Married couple and their married children.
Step 1: Matching the concepts.
The correct matching is:
- Nuclear Family: Mates and their children
- Matrilineal Descent: Children belong to the kin group of mothers
- Fraternal Polyandry: Husbands are brothers
- Extended Family: Married couple and their married children
Final Answer:
\[
\boxed{\text{The correct answer is (3) (A) - (I), (B) - (II), (C) - (III), (D) - (IV).}}
\]