Going to movies, dances, or other events in a group is a good idea for teenagers because, all of the above.
All of the options listed are positive effects towards the teenagers, which make them safe in the situation. Going out with friends does remove the expectation of sexual activity, can reveal a lot about a person, and allows others to get to know each other.
This could vary as any health professional should enjoy working with the population they choose to work with. Despite that, it seems like most likely answer would be children.