The "pivotal force" in the Five Forces model is:

a.Rivalry, because of its centrality in the Structure-Conduct-Performance framework.

b.Bargaining power of suppliers, because supply chain management may be critical for many companies.

c.Any force that is the least beneficial (= most detrimental) to the industry incumbents, which thus constrains the average profitability levels.

d.Any force that the industry analysts and managers predict to undergo sudden and dramatic changes in any direction (higher or lower), in the near future.