- Polygyny is a man having multiple wives.
- Sororal polygyny is when a man marries two or more sisters.
- Polyandry is a woman marrying multiple men, sometimes practiced in cultures with scarce resources where brothers share a wife.
- Group Marriage is a system where multiple men and women are married to each other.
Step 1: Understanding Polyandry.
Polyandry, while less common, is observed in some Tibetan and Nepalese cultures. It is practiced to prevent the division of family land and resources.
Final Answer:
\[
\boxed{\text{The correct answer is (3) Polyandry.}}
\]