Some college students have joined together to form a rock band. this band consists of people who have similar interests and a passion for rock music. this group is an example of a (n)

I believe the answer is: subculture

subculture refers to a smaller social group which founded by members from one specific culture that distinguish themselves from other members of the culture with some unique characteristics.

In the example above, the bigger culture is the college environment, the members are the student, the unique characteristics are their love for rock music.