Final answer:
A firm responding to a competitor's market entry by retaliating is considered a competitive driver, seen in various examples like airlines and monopolistic competition scenarios.
Step-by-step explanation:
When a firm responds to a competitor's move by retaliating, as in the case of Linde Gas entering the French market after Air Liquide entered the U.S. market, this action is known as a competitive driver. Competitive drivers are one of the dynamics in international business where firms react to each other's strategic moves. In the examples provided, such as the large airline lowering prices to drive out the smaller start-up or businesses trying to monopolize customer share in monopolistic competition, we see this competitive behavior in practice. Predatory pricing is an extreme form of competitive driver where an established business drops prices to a level where a new competitor cannot survive financially, to ultimately force them out of the market before raising prices again.