Final answer:
Option D, in which a customer won by one company is lost by another, best exemplifies a zero-sum game, where one party's gain equals another's loss.
Step-by-step explanation:
The best example of a zero-sum game is found in option D: Every customer that Mega Incorporated wins over is a customer that one of its competitors loses. In the zero-sum game concept, gains and losses are perfectly balanced by each other, meaning the gain of one player is exactly equal to the loss of another player. This situation reflects the principle that there is a fixed pie of resources or opportunities, so that one party's gain results in another party's loss, just as Brawley describes in his definition of a zero-sum game in the context of gold acquisition among countries.