Curtis Attends a Large University and Knows Very Few People

Curtis attends a large university and knows very few people in his classes. In his sociology class, however, he was required to meet weekly with a group of four other people to work on a term project. After the term was over, they kept meeting weekly to discuss classes and life at university. What type of social group do Curtis and the others make?

A) a primary group
B) a secondary group
C) an interest group
D) an out-group