Public relations can be best defined as:

Public relations is best defined as a broad set of communication efforts to maintain relationships with stakeholders because it encompasses a variety of activities aimed at fostering a positive image and building mutually beneficial relationships with different groups, including customers, employees, investors, and the media. This involves ongoing dialogue and communication strategies designed to create and maintain trust and goodwill.

Public relations is not just about promoting a single product or event; rather, it focuses on the overall reputation and brand perception of an organization over time. This includes activities such as press releases, community engagement, crisis management, and media relations, all of which are crucial for sustaining positive stakeholder relationships.

The other choices reflect narrower concepts: a product demonstration focuses solely on explaining or showcasing a specific product, a one-off promotional event is limited to a temporary marketing tactic, and a sales technique involves specific actions aimed at closing sales rather than broader relationship building. Therefore, the comprehensive nature of public relations as it relates to maintaining and nurturing stakeholder relationships makes it the most accurate definition.