Final answer:
George was engaging in play with Nate by racing cars on a racetrack, which is a form of childhood development and socialization.
Step-by-step explanation:
George was engaging in play with Nate by racing cars on a racetrack. The term 'playing' refers to a voluntary, enjoyable activity that is not serious, which is what George was doing when he continued to play with Nate after their initial race. Play is a crucial part of childhood development, helping in socialization, learning, and emotional growth. In this context, George might be a caregiver, parent, peer, or someone involved in a therapeutic or educational setting, facilitating an environment for Nate to learn and grow through play.