What defines an Unrestricted Free Agent in the NBA?

An Unrestricted Free Agent in the NBA is defined as a player who is free to sign with any team without restriction. This means that once a player's contract expires, they are not bound by any obligations to their previous team and can negotiate and sign with any team in the league that offers a contract. This flexibility allows the player to seek the best possible opportunity, whether that be for financial reasons, team success, or personal preferences.

In contrast, a franchise tag is associated with restricted circumstances that apply to some players under specific contractual conditions, which does not pertain to unrestricted free agency. Similarly, the notion that a player can only sign with their current team describes a situation typically related to either players under contract or restricted free agents who have certain limitations on their signing rights, neither of which applies to unrestricted free agents. Lastly, while a player's contract having expired is one aspect leading them to become an unrestricted free agent, it is the absence of restrictions on their signing choices that truly defines the status. Thus, the hallmark of an unrestricted free agent is the ability to engage with any team freely, marking option C as the correct choice.