Final answer:
The NBA (National Basketball Association) has the highest average salaries for pro athletes among the four major American sports leagues, with star players earning tens of millions annually.
Step-by-step explanation:
The average salaries for professional athletes vary across different sports leagues, with each league having its own pay structure and financial dynamics. In the context of the four major American sports leagues, which comprise the NFL, MLB, NBA, and NHL, the NBA (National Basketball Association) is known for having some of the highest average salaries. NBA players like Stephen Curry command salaries in the tens of millions, with Curry earning around $43 million a year, while even the lowest-paid NBA players earn just over $200,000. In contrast, other leagues may have a different salary range, but the NBA stands out with its high average earnings.