Concept:Producers of identical goods can unite to strengthen their bargaining power in international markets.Explanation:A cartel or monopoly is formed when countries producing the same or identical goods agree to coordinate their output, pricing, or trade policies.This joint action gives them greater leverage when negotiating with other countries or buyers.By acting together, they can secure better deals than they could individually.Classic examples include oil-producing nations that form cartels to control supply and influence prices.Answer:D. Countries producing same or identical goods.