A) Cross-market retaliation is an attack on a competitor's other markets if this competitor attacks a firm's original market.
Cross-market retaliation refers to the firm's response to the competitive action of a rival firm, where the firm attacks the competitor's other markets with the goal of hurting the competitor's overall performance. This type of retaliation occurs when two firms have high market commonality and high multimarket dependency, which means they compete in several markets and depend on each other in those markets. By attacking a competitor's other markets, a firm can potentially weaken its competitor's overall performance and protect its market share.