Final answer:
The relationship described between Pat and Terry, characterized by emotional closeness with consent for outside sexual relationships, best fits the description of a polyamorous relationship.
Step-by-step explanation:
Based on the description of Pat and Terry's relationship, where they are emotionally close and committed to each other yet tolerant of having sexual relationships with others, the best classification for their relationship would be C. Polyamorous. Polyamory is the practice of engaging in multiple romantic relationships with the consent of all the people involved. It is different from polygamy, which traditionally refers to having multiple spouses and is often associated with marriage.
Unlike monogamy, which involves exclusivity to one partner, polyamory allows for open romantic connections with more than one person. Polyamorous relationships are based on a foundational agreement that having romantic or sexual relationships with other people does not diminish the commitment or emotional connection between the involved partners.