According to Virginia law, "Every relationship in which a real estate licensee acts for or represents a person by such person's express authority in a real estate transaction," is considered to be a/an

The correct choice is an agency relationship. In Virginia real estate law, an agency relationship is defined as a fiduciary relationship that exists when a real estate licensee acts on behalf of a principal—someone who has given express authority for the agent to represent them in a transaction. This relationship is foundational in real estate transactions, as it establishes the duties and responsibilities of the agent towards the principal, including loyalty, disclosure, and accounting.

The agency relationship is formally recognized and governed by law, which means the actions taken by the licensee on behalf of the principal must align with the principal's best interests. This relationship is a key concept in real estate practice, as it guides the conduct of agents and ensures accountability in the representation of clients.

In contrast, contractual obligations refer to specific agreements made between parties, a lessee relationship pertains specifically to rental agreements and tenant rights, and a trust involves the management of property or assets by one party for the benefit of another. While these concepts may intersect with agency relationships, they do not accurately capture the definition provided by Virginia law regarding the authority granted by a principal to a licensee in real estate transactions.