Final answer:
The claim is that sports teams should not be based on age, as mixed-age play fosters friendships and physical benefits. Youth sports are important for community-building and positive development, with programs like NFL's Play 60 encouraging inclusive play.
Step-by-step explanation:
The claim in the student's question is: sports teams should not be based on age. This claim suggests that by allowing children of different ages to play together in sports, they can form great friendships, become more flexible, and nimble. The sports journal references and the statement about professional athletes growing up playing in diverse groups support this claim. Furthermore, youth sports are seen as community-building initiatives and a means for kids to engage in positive activities, as exemplified by programs like the NFL's Play 60. Additionally, the personal anecdote about playing with a younger sibling illustrates the benefits and practicality of mixed-age sports teams.