Final answer:
Selling a franchise typically creates the most capital gain for professional sports team owners due to the significant appreciation of sports teams' value over time.
Step-by-step explanation:
The question pertains to what activity typically creates the most capital gain for professional sports team owners. Given the options presented, selling a franchise often results in the most significant capital gain. The sale of a professional sports franchise can result in a substantial one-time capital gain given the high valuations of sports teams which tend to appreciate significantly over time. This gain is typically much larger than the incremental income generated from low player salaries, advertising sales, or tax breaks. For example, if a team was purchased for $100 million and sold for $500 million, the capital gain would be $400 million (minus any associated costs).
It's important to note the contrast with other forms of profit which generally accrue over time and are subject to ongoing operational expenses and taxes. While low salaries for players, selling advertising, and tax breaks can increase profitability, they do not usually result in a dramatic lump sum gain the way the sale of an entire franchise does.