Final answer:
Football is the sport that accounts for 40.5% of concussions among youth, mainly due to the contact nature of the game despite efforts by the NCAA and NFL to mitigate these risks.
Step-by-step explanation:
The sport that constitutes 40.5% of concussions among youth is football (A). Football is a contact sport with a higher risk of head injuries compared to other sports. The NCAA and NFL have recognized these risks and have implemented protocols and equipment ratings to try to reduce the incidence of traumatic brain injuries. Despite these efforts, football remains a sport with a significant number of concussions due to the nature of the game.