Final answer:
The role of children's and adolescents' sense of self in their behavior is best reflected in teenagers participating in team sports activities.
Step-by-step explanation:
The best example of the role that children's and adolescents' sense of self plays in their behavior is B) A teenager participating in a team sports activity. When teenagers participate in team sports, they develop a sense of identity and a feeling of belonging to a group. They become motivated to perform well and work together with their peers towards a common goal. This sense of self and group identity can greatly influence their behavior both on and off the field.