Final answer:
Imitation of competitors (option D) is the one strategy that cannot be used effectively to counter competitive forces since it does not provide a unique value proposition and can lead to legal issues.
Step-by-step explanation:
All of the following strategies can be used to counter competitive forces in the marketplace except imitation of competitors. This is because while strategies like product differentiation, reducing prices, and increasing switching costs can provide a competitive edge, simply imitating competitors does not contribute to a unique value proposition and can even lead to legal issues concerning trademarks or trade secrets. For monopolistically competitive firms, establishing a strong brand and differentiating products are critical moves for increasing demand, whereas direct imitation lacks the creation of market barriers or distinctiveness.