Explanation:

Let’s break it down:

- Option 1: Companionate marriage

This is a marriage based on mutual affection, friendship, and equality. The partners support each other's personal growth. It’s not called a privileged relationship.

- Option 2: Experimental marriage

This term refers to couples living together to test compatibility, sometimes without formal commitment. Again, “privileged relationship” isn’t the label here.

- Option 3: Hypergamy

Hypergamy is when someone marries "up"—choosing a partner from a higher social or economic class. It's about social mobility, not privileged legal or social status as a relationship type.

- Option 4: Levirate

Levirate marriage is when a man marries the widow of his deceased brother. This is often seen as a privileged relationship in many traditional societies because it’s given a special status and rights for lineage and property reasons.

Correct Answer: Option 4, Levirate is what’s known as a privileged relationship.

The idea is, the levirate marriage comes with social or legal privileges specifically to maintain family structure and inheritance rules. The others don't quite fit that description.