Answer: b) Reference group
Explanation:
Reference group is defined as collection of members with which other person or the group is evaluated and compared .The other group tends to measure their behavior and abilities through comparing with the reference group.
Michael's basketball team can be considered as his reference group because he is gaining cues for behavior in hallway , classroom and dance through evaluating the team's behavior.
Other options are incorrect because out-group are the members out of a specific group.Aggregate is are people who are present at same time and place but do not persist any link. Secondary group is the group where personal interaction is low and work move towards goal.
Thus, the correct option is option(b).