Answer:
C. a religious subculture
Explanation:
Celia belonged to the religious subculture in high school. Most religions can also be seen as subcultures in society. They can be classified this way because they make the specific community of the believers who use their religion as the dominant factor of their identity. Religious teaching and rituals have an influence on the life and behavior of the participants, organizing their time, diet, philosophies, and practices.
This means that Celia was not only a believer but a part of the culture of a certain community that practiced the same behavior and manners.