Which of the following is an example of anti-trust behavior?

Anti-trust behavior refers to actions that restrict competition in a market, often leading to monopolistic practices or collusion among businesses. In this case, agreeing with other brokerage agencies to boycott a vendor, such as a newspaper, exemplifies anti-trust behavior because it involves a collective decision to eliminate or hinder competition—a critical violation of anti-trust laws. By coordinating a boycott, the agencies are attempting to exert their influence in a way that disrupts the normal competitive landscape, potentially harming the vendor's business and the choices available to consumers.

The other scenarios do not illustrate anti-trust behavior. Collaborating with other agencies for charitable purposes encourages community engagement without affecting competition. Meeting a designated broker for lunch is a standard networking practice that does not involve competitive agreements. Forming a joint venture to sell real estate involves cooperation for mutual benefit and may not inherently limit competition unless structured in an anti-competitive manner. Therefore, the choice of boycotting a vendor is the clearest violation of anti-trust principles, clearly highlighting the nature of collusion that is prohibited by law.