Final answer:
A primary group is a small, close-knit group with intimate and long-term emotional relationships, like a family or friends. A sorority or fraternity, due to its emotionally close relationships and long-term commitment, is most likely to constitute a primary group.
Step-by-step explanation:
When considering a primary group, the term is defined by sociologist Charles Horton Cooley as a small, intimately connected group that fulfills emotional and expressive needs, generally engaging in face-to-face, long-term emotional relationships. Examples include families and close friend circles. Given the options, your sorority or fraternity is most likely to constitute a primary group due to the complex relationships, close ties, and significant impact on socialization they foster, often resembling a family unit. While a class study group or work group may initially be more task-focused and serve instrumental functions more akin to secondary groups, they have the potential to evolve into primary groups over time if deeper personal connections develop.